Showing papers on "Bicyclic molecule published in 2006"
TL;DR: The gold(I) catalyzed rearrangement of 5-en-2-yn-1-yl acetates into functionalized acetoxy bicyclo[3.1.0]hexenes is described, which allows the efficient and rapid synthesis of a variety of such bicyclic compounds via a sequence of twoGold(I)-catalyzed isomerization steps.
Abstract: The gold(I) catalyzed rearrangement of 5-en-2-yn-1-yl acetates into functionalized acetoxy bicyclo[3.1.0]hexenes is described. The mild reaction conditions employed allow the efficient and rapid synthesis of a variety of such bicyclic compounds via a sequence of two gold(I)-catalyzed isomerization steps. Acetoxy bicyclo[3.1.0]hexenes products can be further transformed to 2-cycloalkenones by simple methanolysis.
243 citations
TL;DR: Although high enantioselectivities were obtained in the hydrogenation of certain trisubstituted aryl alkenes such as (E)-methylstilbene, the application range of Ir-phox catalysts proved to be limited, and subsequent work has led to new classes of N,P ligands, which have broadened the scope ofIr-catalyzed asymmetric hydrogenation considerably.
Abstract: Iridium complexes with chiral N,P ligands have established themselves as efficient catalysts for the asymmetric hydrogenation of olefins, with largely complementary scope to Rh and Ru diphosphane complexes. In contrast to Rh and Ru catalysts, they do not require a coordinating polar group next to the C=C bond. Initial experiments with cationic phosphanyloxazoline (phox) complexes ([Ir(1)(cod)]X ) (cod= cyclooctadiene) showed that these catalysts are highly active in the hydrogenation of unfunctionalized triand even tetrasubstituted olefins. In this respect, they resemble Crabtree)s catalyst, [(Cy3P)(pyridine)Ir(cod)]PF6 (Cy= cyclohexyl), which provided the stimulus for the development of these catalysts. In these studies, we also found that the choice of solvent and anion is crucial as only in weakly coordinating solvents like dichloromethane or toluene with a virtually non-coordinating anion such as BArF (tetrakis[bis3,5-(trifluoromethyl)phenyl]borate) could high turnover numbers (> 5000) be obtained. Although high enantioselectivities were obtained in the hydrogenation of certain trisubstituted aryl alkenes such as (E)-methylstilbene, the application range of Ir-phox catalysts proved to be limited. However, subsequent work has led to new classes of N,P ligands, which have broadened the scope of Ir-catalyzed hydrogenation considerably. 7] Among the many structures we investigated, oxazolinephosphinites such as 3 and certain imidazoline analogues proved to be particularly efficient, giving high enantiomeric excesses with a wide range of unfunctionalized as well as certain functionalized olefins. With the intention of mimicking the coordination sphere of the Crabtree catalysts more closely, we also examined a series of pyridineand quinoline-derived ligands 4 and 5. As the results were quite encouraging, we decided to extend our studies to bicyclic analogues of type 6 because we thought that the more rigid conformation imposed by the additional ring could result in even higher enantioselectivities. Here we report the syntheses of a series of pyridyl–phosphinites 6 and their evaluation as ligands for Ir-catalyzed asymmetric hydrogenation. As shown in the schemes below, ligands of this type are readily accessible from simple, commercially available starting materials via the corresponding pyridyl alcohols. By changing the substituents at the pyridine ring and the P atom, or altering the size of the carbocyclic ring, the steric and electronic properties of these ligands and the coordination geometry can be optimized for a specific substrate. Ligands with unsubstituted backbones (6, R=H) were synthesized from commercially available precursors 12–14 via pyridyl alcohols 7–9 (Scheme 1). Oxidation to the corre-
235 citations
TL;DR: This is the first case of a highly enantioselective base-catalyzed anthrone Diels-Alder reaction, and it was found that several anthrone derivatives suitable for this reaction were obtained.
Abstract: Chiral bicyclic guanidine 1 was found to be an excellent catalyst for reactions between anthrones and various dienophiles. The catalyst can tolerate a range of substituents and substitution patterns, making several anthrone derivatives suitable for this reaction. Both Diels−Alder and Michael adducts were obtained in excellent yields, high regioselectivities, and high enantioselectivities. This is the first case of a highly enantioselective base-catalyzed anthrone Diels−Alder reaction.
175 citations
171 citations
TL;DR: In this paper, the electronic properties of an unusually redox-rich iron system, [PhBPR 3]FeNx, are explored by Mossbauer, EPR, magnetization, and density-functional methods to gain a detailed picture regarding their oxidation states and electronic structures.
Abstract: The electronic properties of an unusually redox-rich iron system, [PhBPR 3]FeNx (where [PhBPR 3] is [PhB(CH2PR2)3]−), are explored by Mossbauer, EPR, magnetization, and density-functional methods to gain a detailed picture regarding their oxidation states and electronic structures. The complexes of primary interest in this article are the two terminal iron(IV) nitride species, [PhBPiPr 3]FeN (3a) and [PhBPCH2Cy 3]FeN (3b), and the formally diiron(I) bridged-Fe(μ-N2)Fe species, {[PhBPiPr 3]Fe}2(μ-N2) (4). Complex 4 is chemically related to 3a via a spontaneous nitride coupling reaction. The diamagnetic iron(IV) nitrides 3a and 3b exhibit unique electronic environments that are reflected in their unusual Mossbauer parameters, including quadrupole-splitting values of 6.01(1) mm/s and isomer shift values of −0.34(1) mm/s. The data for 4 suggest that this complex can be described by a weak ferromagnetic interaction (J/D < 1) between two iron(I) centers. For comparison, four other relevant complexes also are characterized: a diamagnetic iron(IV) trihydride [PhBPiPr 3]Fe(H)3(PMe3) (5), an S = 3/2 iron(I) phosphine adduct [PhBPiPr 3]FePMe3 (6), and the S = 2 iron(II) precursors to 3a, [PhBPiPr 3]FeCl and [PhBPiPr 3]Fe-2,3:5,6-dibenzo-7-aza bicyclo[2.2.1]hepta-2,5-diene (dbabh). The electronic properties of these respective complexes also have been explored by density-functional methods to help corroborate our spectral assignments and to probe their electronic structures further.
149 citations
TL;DR: This reaction employing cyclobutanones as a C4 unit constructs cyclooctadienone cores in one synthetic step and forms a nine-membered nickelacycle.
Abstract: Cyclobutanones underwent a formal [4 + 2 + 2] annulation reaction with 1,6- and 1,7-diynes in the presence of nickel(0) catalysts to provide bicyclic eight-membered ring ketones. The annulation reaction proceeds through a ring-expansion of oxanickelacycloheptadiene via β-carbon elimination to form a nine-membered nickelacycle. This reaction employing cyclobutanones as a C4 unit constructs cyclooctadienone cores in one synthetic step.
138 citations
TL;DR: A series of 2,5,6-trisubstituted and 2,1-b][1,3,4]thiadiazoles were synthesized and screened for antitubercular activity against Mycobacterium tuberculosis H37Rv, antibacterial activity against Escherichia coli and Bacillus cirrhosis, and antifungal activity against Aspergillus niger and Penicillium wortmanni.
125 citations
TL;DR: Synthesized triazolo thiadiazoles investigated for their antibacterial, antifungal, anti-inflammatory and analgesic activities showed moderate antimicrobial activity against various tested bacterial and fungal strains.
124 citations
TL;DR: It is proposed that the 2'-oxygen atom of the bicyclic moiety is essential for the formation of stabilized A-type-like dsDNA but not for theformation of a stabilized A -type DNA:RNA hybrid.
Abstract: Two bicyclic 2‘-deoxynucleoside analogues containing a saturated and an unsaturated three-carbon 2‘,4‘-linkage, respectively, have been synthesized using a ring-closing metathesis-based linear strategy starting from uridine Both analogues have been incorporated into oligodeoxynucleotide sequences and increased the stability of DNA:RNA hybrid duplexes (ΔTm ∼ 25−50 °C per modification) and decreased the stability of dsDNA duplexes (ΔTm ∼ 25−10 °C per modification) CD spectroscopy revealed that the bicyclic nucleosides induced formation of A-type-like duplexes albeit to a lesser degree than found for locked nucleic acid (LNA) monomers From the CD data and UV melting analysis, we propose that the 2‘-oxygen atom of the bicyclic moiety is essential for the formation of stabilized A-type-like dsDNA but not for the formation of a stabilized A-type DNA:RNA hybrid
123 citations
Patent•
28 Jul 2006TL;DR: In this article, the authors presented a list of inhibitors of HCV replication of formula (I) and the Noxides, salts, or stereoisomers thereof, where each dashed line represents an optional double bond.
Abstract: Inhibitors of HCV replication of formula (I) and the N-oxides, salts, or stereoisomers thereof, wherein each dashed line represents an optional double bond; X is N, CH and where X bears a double bond it is C; R1 is -OR6, -NH-SO2R7; R2 is hydrogen, and where X is C or CH, R2 may also be C1-6alkyl; R3 is hydrogen, C1-6alkyl, C1-6alkoxyC1-6alkyl, or C3-7cycloalkyl; n is 3, 4, 5, or 6; R4 and R5 taken together with the nitrogen atom to which they are attached form a bicyclic ring system selected from formula (II) wherein said ring system may optionally be substituted with 1-3 substituents; R6 is hydrogen; aryl; Het; C3-7cycloalkyl optionally substituted with C1-6alkyl; or C1-6alkyl optionally substituted with C3-7cycloalkyl, aryl or with Het; R7 is aryl; Het; C3-7cycloalkyl optionally substituted with C1-6alkyl; or C1-6alkyl optionally substituted with C3-7cycloalkyl, aryl or with Het; aryl is phenyl or naphthyl, each of which may be optionally substituted with 1-3 substituents; Het is a 5 or 6 membered saturated, partially unsaturated or completely unsaturated heterocyclic ring containing 1 to 4 heteroatoms each independently selected from N, O or S, and being optionally substituted with 1-3 substituents pharmaceutical compositions containing compounds (I) and processes for preparing compounds (I). Bioavailable combinations of the inhibitors of HCV of formula (I) with ritonavir are also provided.
122 citations
TL;DR: The asymmetric variant of this reaction, enantioselective desymmetrization of substituted malononitriles, also proceeded to give enantio-enriched bicyclic pyridines which possess a tertiary or quaternary stereocenter as discussed by the authors.
TL;DR: Treatment of cyclic imines with 3,3'-disubstituted binaphthol modified allylboronates provides the expected allylated products in good yields and with high stereoselectivities.
Abstract: Treatment of cyclic imines with 3,3‘-disubstituted binaphthol modified allylboronates provides the expected allylated products in good yields and with high stereoselectivities (91−99% ee). The products may be readily transformed into various alkaloids.
TL;DR: Careful screening of nitrile components revealed that a C[triple chemical bond]C triple bond or heteroatom substituents, such as methoxy and methylthio groups, proved to act as the coordinating groups, whereas C==C or C==O double bonds and amino groups failed to promote cycloaddition.
Abstract: In the presence of a catalytic amount of [Cp*RuCl(cod)] (Cp*=pentamethylcyclopentadienyl, cod=1,5-cyclooctadiene), 1,6-diynes were allowed to react chemo- and regioselectively with nitriles bearing a coordinating group, such as dicyanides or alpha-halonitriles, at ambient temperature to afford bicyclic pyridines Careful screening of nitrile components revealed that a C[triple chemical bond]C triple bond or heteroatom substituents, such as methoxy and methylthio groups, proved to act as the coordinating groups, whereas C==C or C==O double bonds and amino groups failed to promote cycloaddition This suggests that coordinating groups with multiple pi-bonds or lone pairs are essential for the nitrile components
TL;DR: In this article, the 1,1-organoboration reactions tolerate various functional groups at the alkyne as well as at the metal, and the characterization of intermediates and final products by X-ray structural analysis and by multinuclear magnetic resonance spectroscopy (NMR).
Abstract: Metallacyclopentadienes (metalloles) containing M = Si, Ge, Sn, Pb, Ti, Pt can be prepared by 1,1-organoboration of alkyn-1-ylmetal compounds LnMCCR1(R1 = H, alkyl, aryl, silyl, etc; L depends on M, and can be hydrogen, alkyl, aryl, Cl, Br, amino groups, a chelating diphosphane, and one or more L can be again alkynyl groups). These reactions proceed via activation of the MC bond(s) by an electron-deficient triorganoborane BR3 (R = alkyl, aryl; non-cyclic, monocyclic, bicyclic, and tricyclic boranes), at first intermolecular and then intramolecular. In the course of these reactions, the MC bonds are cleaved, zwitterionic alkynylborate-like intermediates are formed, in which the metal-containing fragments are coordinated side-on to the CC bonds. In most cases, the 1,1-organoboration reactions tolerate various functional groups at the alkyne as well as at the metal. The characterization of intermediates and final products by X-ray structural analysis and by multinuclear magnetic resonance spectroscopy (NMR) is documented and described. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:188–208, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20222
TL;DR: The use of TADDOL-based phosphoramidite ligands on rhodium allows for the incorporation of terminal alkynes in the [2+2-2] cycloaddition with alkenyl isocyanates, which leads to an expedient asymmetric total synthesis of the alkaloid lasubine II.
Abstract: The use of TADDOL-based phosphoramidite ligands on rhodium allows for the incorporation of terminal alkynes in the [2+2+2] cycloaddition with alkenyl isocyanates. Terminal aliphatic alkynes provide bicyclic lactams, while the use of aryl alkynes provides complementary access to vinylogous amides. Product selectivity seems to be governed by a combination of electronics and sterics, with smaller and/or more electron-deficient substituents favoring lactam formation. The use of homologous alkenyl isocyanates leads to an expedient asymmetric total synthesis of the alkaloid lasubine II.
TL;DR: A novel tandem Pd-catalyzed cross-coupling and [4 + 4] cycloaddition sequence allows the rapid synthesis of eight-membered carbocycles starting from alpha-bromovinyl arenes and propargyl bromides in one reaction vessel.
Abstract: A novel tandem Pd-catalyzed cross-coupling and [4 + 4] cycloaddition sequence allows the rapid synthesis of eight-membered carbocycles starting from α-bromovinyl arenes and propargyl bromides in one reaction vessel. It is noteworthy that four components are assembled into one molecule via this procedure. In contrast to α-bromovinyl arenes, α-bromovinyl alkanes afforded tandem cross-coupling and homo [4 + 2] cycloaddition products. Subjecting an equimolar mixture of α-bromostyrene and 2-bromo-1-octene to propargyl bromides furnished the tandem Pd-catalyzed cross-coupling and hetero [4 + 2] cycloaddition product. Exposure of equimolar mixtures of α-bromovinyl arenes to allenylindium resulted in tandem a Pd-catalyzed cross-coupling and hetero [4 + 4] cycloaddition products. Synthesis of vinylallene from the reaction of vinyl triflate with allenylindium followed by Pd-catalyzed carbon monoxide insertion reaction gave the corresponding 3,7-nonadienone product via tandem Pd-catalyzed cross-coupling and [4 + 4 +...
TL;DR: In this paper, a new catalyst for the cycloaddition of α,ω-diynes with monoynes was found to give polysubstituted benzene derivatives in high yields.
Abstract: [Ir(cod)Cl]2/DPPE was found to be a new catalyst for the cycloaddition of α,ω-diynes with monoynes to give polysubstituted benzene derivatives in high yields. Internal monoynes as well as terminal monoynes could be used. The reaction tolerates a broad range of functional groups such as alcohol, amine, alkene, ether, halogen, and nitrile. The reaction of 1,6-octadiyne derivatives with 1-alkynes gives ortho products and meta products. The regioselectivity could be controlled by the choice of ligand. The reaction with DPPE was meta selective, with meta selectivity of up to 82%. The reaction with DPPF was ortho selective, with ortho selectivity of up to 88%. We propose a mechanism to account for this regioselective cycloaddition. [Ir(cod)Cl]2/DPPE also catalyzed the cycloaddition of α,ω-diynes with 2,5-dihydrofuran to give bicyclic cyclohexadiene derivatives. The reaction with 2,3-dihydrofuran and n-butyl vinyl ether gave benzene derivatives instead of cyclohexadiene derivatives. We also propose a mechanism t...
TL;DR: A highly diastereoselective, nucleophile-promoted bis-cyclization process, employing readily available and tractable keto acid substrates, is described, which provides concise access to bicyclic- and tricyclic-beta-lactones bearing tertiary carbinol centers and quaternary carbons.
TL;DR: New C2-symmetric bicyclo[2.2.1]hepta-2,5-dienes bearing methyl and phenyl substituents at the 2 and 5 positions were prepared enantiomerically pure through a two-step sequence starting from the readily available bicyclo(diene)2-dione due to the instability or volatility of these dienes.
Abstract: New C2-symmetric bicyclo[2.2.1]hepta-2,5-dienes bearing methyl and phenyl substituents at the 2 and 5 positions were prepared enantiomerically pure through a two-step sequence starting from the readily available bicyclo[2.2.1]hepta-2,5-dione. Due to the instability or volatility of these dienes, their isolation was achieved through the formation of the corresponding stable [RhCl(diene)]2 complexes. These chiral rhodium complexes displayed high activity and enantioselectivity (up to 99% ee) in the rhodium-catalyzed 1,4-addition and 1,2-addition of phenylboronic acid to cyclic enones and N-sulfonylimines, respectively.
Patent•
22 Dec 2006TL;DR: In this paper, the general formula (I) in which the variable groups are as defined herein, and their preparation and use is described. But this work is restricted to compounds of I.
Abstract: This invention relates to compounds of the general formula (I) in which the variable groups are as defined herein, and to their preparation and use.
TL;DR: In this paper, the diphenylacetylene complex Os(PhC⋮CPh)(CS)(PPh3)2 (1) and two molecules of HC ⋮CCO2Me leads to a very stable, blue, osmabicylic complex with osmium at a bridgehead position.
TL;DR: Using a B-alkyl Suzuki cross-coupling as a key step, a concise and stereocontrolled synthesis of five- to eight-membered triisopropylsiloxy ethers having (2Z)-(6,6-dimethoxyhexylidene) or (5,5-Dimethoxypentylidenes) side chains was developed, with high stereo- and enantioselectivity.
Abstract: Using a B-alkyl Suzuki cross-coupling as a key step, a concise and stereocontrolled synthesis of five- to eight-membered triisopropylsiloxy ethers having (2Z)-(6,6-dimethoxyhexylidene) or (2Z)-(5,5-dimethoxypentylidene) side chains was developed. Prins-pinacol reactions of these precursors promoted by SnCl4 provide bicyclic products in which 5-, 6-, or 7-membered rings are joined by a C−C single bond. Synthetically challenging attached ring systems in which both rings are chiral can be prepared in this fashion with high stereo- and enantioselectivity. Stabilizing through-space electrostatic interactions between the α-alkoxycarbenium ion and an axially positioned oxygen substituent are believed to play a significant role in organizing the transition structure of the Prins cyclization.
TL;DR: In this paper, the synthesis of polysilanes with potassium alkoxides was found to be superior to analogous chemistry using methyllithium, and polysilano compounds were used to prepare a number of transition metal compounds, including the first example of an early transition metal disilene complex.
TL;DR: The results suggest the possibility of developing novel polymeric prodrugs based on a new release mechanism and a set of 34 AT(1) receptor antagonists was used as a new test for the evaluation of the predictive capability of the previously published qualitative and quantitative pharmacophore models.
Abstract: The 4-phenylquinoline fragment of novel AT1 receptor antagonists 4 based on imidazo[4,5-b]pyridine moiety was replaced by 4-phenylisoquinolinone (compounds 5) or 1-phenylindene (compounds 6) scaffolds to investigate the structure−activity relationships. Binding studies showed that most of the synthesized compounds display high affinity for the AT1 receptor. Because of the in vitro high potency of carboxylic acids 5b,f, they were evaluated in permeability (in Caco-2 cells) and in pharmacokinetic studies in comparison with quinoline derivatives 4b,i,j,k. The studies showed that these compounds are characterized by rapid excretion, low membrane permeability, and low oral bioavailability. The structure optimization of the indene derivatives led to compounds 6e,f possessing interesting AT1 receptor affinities. Optimization produced polymerizing AT1 receptor ligand 6c, which forms a thermoreversible polymer (poly-6c) and is released from the latter by a temperature-dependent kinetics. The results suggest the po...
TL;DR: The inter- and intramolecular couplings of unactivated alkenes to 3,4-dihydroquinazolines with a Rh(I) catalyst are reported and the second total synthesis of vasicoline was achieved.
Abstract: The inter- and intramolecular couplings of unactivated alkenes to 3,4-dihydroquinazolines with a Rh(I) catalyst are reported. Coupling between olefins and NH-3,4-dihydroquinazoline was found to occur consecutively with heterocycle dehydrogenation in the presence of a Rh(I)/PCy3/HCl catalyst. The reaction was used to develop an effective method for the synthesis of 2-substituted quinazolines through an oxidative workup step. The regiocontrolled synthesis and Rh-catalyzed cyclization of alkene-tethered 3,4-dihydroquinazolines are also described. Applying this method, the second total synthesis of vasicoline was achieved. The key Rh-catalyzed cyclization step was made possible by the use of a rigid bicyclic phosphine ligand. The synthesis further demonstrates a challenging Cu-catalyzed amidation of an ortho-substituted aryl chloride.
TL;DR: A facile palladium-catalyzed carbocyclization reaction of aromatic iodides, bicyclic alkenes, and benzynes to furnish various annulated 9,10-dihydrophenanthrene derivatives is described.
Patent•
28 Jul 2006TL;DR: Inhibitors of HCV replication of formula (I) and the N-oxides, salts, and stereoisomers thereof, where each dashed line represents an optional double bond as mentioned in this paper.
Abstract: Inhibitors of HCV replication of formula (I), and the N-oxides, salts, and stereoisomers thereof, wherein each dashed line represents an optional double bond; X is Ν, CH and where X bears a double bond it is C; R1a and R1b are hydrogen, C3-7cycloalkyl, aryl, Het, C1-6alkoxy, C1-6alkyl optionally substituted with halo, C1-6alkoxy, cyano, polyhaloC11-6alkoxy, C3-7cycloalkyl, aryl, or with Het; or R1a and R1b together with the nitrogen to which they are attached form a 4 to 6 membered heterocyclic ring which may be optionally substituted; L is a direct bond, -O- , -O-C1-4alkanediyl-, -O-CO-, -O-C(=O)-ΝR5a - or -O -C(=O)-NR5a-C1-4alkanediyl-; R2 is hydrogen, and where X is C or CH, R2 may also be C1-6alkyl; R3 is hydrogen, C1-6alkyl, C1-6alkoxyC1-6alkyl, C3-7cycloalkyl, amino, mono- or diC1-6alkylamino; R4 is aryl or a saturated, a partially unsaturated or completely unsaturated 5 or 6 membered monocyclic or 9 to 12 membered bicyclic heterocyclic ring system wherein said ring system contains one nitrogen, and optionally one to three additional heteroatoms selected from O, S and N, and wherein the remaining ring members are carbon atoms; wherein said ring system may be optionally substituted; n is 3, 4, 5, or 6; p is 1 or 2; aryl is phenyl, naphthyl, indanyl, or 1,2,3,4-tetrahydronaphthyl, each of which may be optionally substituted with one, two or three substituents; and Het is a 5 or 6 membered saturated, partially unsaturated or completely unsaturated heterocyclic ring containing 1 to 4 heteroatoms selected from N, O and S , being optionally condensed with a benzene ring, and wherein Het may be optionally substituted with one, two or three substituents; pharmaceutical compositions containing compounds (I) and processes for preparing compounds (I).
TL;DR: The standard enthalpies of formation for some of the new salts were calculated by using the computationally feasible DFT(B3LYP) and MP2 methods in conjunction with an empirical approach based on densities of salts.
Abstract: Bicyclic azoles, 2-methyl-5-(imidazol-1-yl)-2H-tetrazole (1), 2-methyl-5-(1,2,4-triazol-1-yl)-2H-tetrazole (4), 1-methyl-5-(imidazol-1-yl)-1H-tetrazole (7), 1-methyl-5-(1,2,4-triazol-1-yl)-1H-tetrazole (10), 1-methyl-4-nitro-2-(imidazol-1-yl)-1H-imidazole (13), and 1-methyl-4-nitro-2-(1,2,4-triazol-1-yl)-1H-imidazole (16) were prepared. Their thermally stable azolium salts, 3, 6, 9, 12, 15, and 18-21, with densities ranging between 1.519-1.674 g cm-3, were synthesized by quaternization with nitric or perchloric acid or with iodomethane followed by metathesis reactions with silver nitrate and silver perchlorate. The structures of 12 b and 21 b were confirmed by single-crystal X-ray analysis. The standard enthalpies of formation for some of the new salts were calculated by using the computationally feasible DFT(B3LYP) and MP2 methods in conjunction with an empirical approach based on densities of salts. The calculated values range from DeltaHdegreef=209.9 (21 a) to 412.3 (12 b) kJ mol-1 in which the experimental densities are >1.515 g cm-3.
TL;DR: A series of chiral bicyclic guanidines, either symmetrical or non-symmetrical, was synthesized using a concise and efficient aziridine-based synthetic methodology, showing moderate enantioselectivity for several Michael reactions.