Showing papers in "Journal of Organic Chemistry in 1993"

Design, synthesis, and control of conducting polymer architectures: structurally homogeneous poly(3-alkylthiophenes)

Abstract: The full details of a facile synthesis of structurally homogeneouspoly(3-alkylthiophene) (PAT's) is presented. In three steps from 3-bromothiophene, PAT's can be made with complete regiochemical control. We define structurally homogenous an a regiochemically well-defined polymer structure that in oar cane contains almsost exclusively head-to-tail couplings (HT-HT) (2,5-couplings between adjacent thiophene rings). By analysis of the NMR data, oar poly(n-butylthiophene) (5a) contains 93% HT-HT couplings, 98% of the desired regiochemistry is found in poly(n-hexylthiophene) (5b), 97% in poly(n-octylthiophene), (5c), and 95% in poly(n-dodecylthiophene), (5d)

New nitric oxide-releasing zwitterions derived from polyamines

Abstract: The reaction of nitric oxide (NO) with polyamines has been studied, resulting in the discovery of a new type of NO-releasing compound having the structure RN[N(O)NO][sup [minus]](CH[sub 2])[sub x]NH[sub 2][sup +]R[prime]. Numerous examples of these zwitterionic polyamine/NO adducts have been prepared and found to be very stable solids which release NO in solution. The new compounds contain as much as 45% NO by weight and are capable of releasing it all at rates which have been shown to vary in a predictable way with structure. The half-lives in buffered aqueous solution at pH 7.4 and 22[degrees]C were shown to vary from extremely short (1.3 min for diamine 8, MeN[N(O)NO][sup [minus]](CH[sub 2])[sub 4]NH[sub 2][sup +]Me) to very long (56 h for triamine 18, H[sub 2]NCH[sub 2]CH[sub 2]N[N(O)NO][sup [minus]]CH[sub 2]CH[sub 2]NH[sub 3][sup +]). In general, the longest half-lives were achieved by triamine/NO adducts and derivatives of ethylenediamine (x = 2). For any given value of x, a small increase in the size of R resulted in a relatively large increase in half-life but changes in R[prime] appeared to have little effect. Data are presented which should allow the selection of the proper compounds to achieve a wide range of desired NO generationmore » rates. These NO-containing zwitterions should prove to be important resources in studies of the biology of NO and may also have important pharmaceutical and chemical applications. 10 refs., 1 tab.« less

A convenient reduction of amino acids and their derivatives

Abstract: The formation of chiral amino alcohols by reduction of amino acids has been the subject of considerable effort due to their importance in asymmetric synthesis? peptide and pharmaceutical chemistry: resolution of racemic mixtures: synthesis of insecticidal compounds: and others. From the earliest reports by Karrer in 1921, amino alcohols were prepared by reduction of the corresponding amino acid esters with sodium in ethanol.& Subsequently, lithium aluminum hydride6b and sodium borohydride& were employed and furthermore, free amino acids were shown to be reduced directly by sodium bis(2-methoxyethoxy)aluminum hydride? the borane-dimethyl sulfide complex activated by boron trifluoride-etherate,w lithium aluminum hydride? lithium borohyride with trimethylchl~rosilane,~~ sodium borohydride-trimethyl~hlorosilane,~g or boron trif l~orideetherate.~~ Very recently, while this manuscript was being prepared, a report appeared describing an efficient reduction of amino acids and derivatives using sodium borohydride and sulfuric

Catalytic activity of various salts in the reaction of 2,3-epoxypropyl phenyl ether and carbon dioxide under atmospheric pressure

Abstract: Reaction of 2,3-epoxypropyl phenyl ether (1) with carbon dioxide was carried out under atmospheric pressure in N-methylpyrrolidinone (NMP) at 100 o C in the presence of 5 mol% of various salts to obtain a five-membered cyclic carbonate, 4-(phenoxymethyl)-1,3-dioxolan-2-one (2), selectively. Only side salts showed high catalytic activity, and the order of intrinsic activity was found to be as follows: chloride>bromide>iodide which is the order of nucleophilicity of the anion. Furthermore, the order of the activity was found to be lithium salt>sodium salt> benzyltrimethylammonium salt, which is in accord with the order of Lewis acidity of the cation. Kinetic analyses show that the reaction rate can be represented by -d[1]/dt=k[1][cat.], where the carbon dioxide pressure shows no effect on the reaction rate

Ulosantoin, a potent insecticide from the sponge Ulosa ruetzleri

Abstract: Ulosantoin (2), a phosphorylated hydantoin, has been isolated from organic soluble extracts of the sponge Ulosa ruetzleri and found to exhibit marked insecticidal activity against tobacco hornworm larvae and cockroaches. The structure was determined by X-ray diffraction analysis. A structurally related compound, dimethyl N 2 -creatininylphosphate (1), was also isolated from the sponge extracts, but was inactive in the insecticidal screens

Analysis of two carbon-13 NMR correlations for determining the stereochemistry of 1,3-diol acetonides

Abstract: The stereochemistry of syn- and anti-1,3-diol acetonides can be assigned from the 13 C chemical shifts of the acetal methyl groups and from the 13 C chemical shifts of the acetal carbon. In general, the syn-1,3-diol acetonides have acetal methyl shifts at 19 and 30 ppm and acetal carbon shifts at 98.5 ppm, while the anti-acetonides have methyl shifts at 25 ppm and acetal shifts at 100.5 ppm. We have tested the generality and reliability of these two correlations by carrying out a complete literature search for 1,3-diol acetonides and identifying those with assignable 13 C spectra

Palladium-catalyzed cross-coupling reaction of organoboron compounds with organic triflates

Abstract: The cross-coupling reaction of 9-alkyl-9-borabicyclo[3.3.1]nonane (9-R-9-BBN), 1-alkenyl-1,3,2-benzodioxaborole, or aryl boronic acid with 1-alkenyl or aryl triflates in the presence of K 3 PO 4 (1.5 equiv) and a catalytic amount of Pd(PPh 3 ) 4 or Cl 2 Pd(dppf) resulted in high yields. The reaction conditions are sufficiently mild so that a variety of functionalized alkenes, alkadienes, and arenes are readily obtained. The utility of the present reaction was demonstrated by the cyclization of ω-alkenyl triflates leading to a benzo-fused cycloalkene and bicyclic alkene via a hydroboration-intramolecular coupling sequence

A rapid screening test to determine the antioxidant potencies of natural and synthetic antioxidants

Abstract: This paper presents a simple and convenient method for measuring antioxidant efficiencies in a model system consisting of micelles of sodium dodecyl sulfate (SDS) with added linoleic acid. The analytical method involves following the development of absorption at 230 nm due to the conjugated diene hydroperoxide of linoleic acid; 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP) is used as the initiator. The antioxidant efficiency of an antioxidant is defined as AE=k inh /k p , where k inh is the rate constant for reaction of the peroxyl radical from linoleic acid with the antioxidant (eq 7 in the text) and k p is the propagation rate constant for autoxidation of linoleic acid (eq 5)

Direct conversion of activated alcohols to azides using diphenyl phosphorazidate. A practical alternative to mitsunobu conditions

Abstract: Fourteen alcohols were converted to their corresponding azides with inversion of configuration using diphenyl phosphorazidate and DBU

Synthesis of aryl- and vinylacetylene derivatives by copper-catalyzed reaction of aryl and vinyl iodides with terminal alkynes

Abstract: The coupling reaction of aryl iodides with terminal alkynes by using a catalyst system of CuI-PPh 3 in the presence of K 2 CO 3 as base gives the corresponding arylated alkynes in excellent yields. Addition of PPh 3 is essential for the reaction to proceed catalytically. Vinyl iodides also react smoothly with the alkynes to give enyne compounds with retention of the configurations. While DMF and DMSO can be used as solvents, DMSO is found to be effective for the reaction with aliphatic terminal alkynes. A reaction mechanism involving initial formation of copper acetylide species coordinated by PPh 3 followed by reaction of aryl and vinyl iodides is proposed

Synthesis of indenones via palladium-catalyzed annulation of internal alkynes

Abstract: A number of 2,3-disubstituted 1-indenones have been prepared in fair to good yields by treating o-iodo- or o-bromobenzaldehyde with various internal alkynes in the presence of a palladium catalyst. Synthetically, the methodology provides an especially convenient route to stable hindered indenones containing aryl, silyl, and tert-alkyl groups. The reaction is believed to proceed through a palladium-(IV) intermediate, and the regiochemistry of the reaction is controlled sterically

Facile elaboration of porphyrins via metal-mediated cross-coupling

Abstract: Metal-mediated cross-coupling methodologies have been successfully employed to porphyrinic systems, providing a powerful, versatile, and general synthetic approach for the fabrication of elaborated porphyrin structures

One-pot synthesis of trifluoroacetimidoyl halides

Abstract: Trifluoroacetimidoyl chlorides 1 were obtained in 80-90% yields when a mixture of trifluoroacetic acid and a primary amine was heated in carbon tetrachloride in the presence of triphenylphosphine and triethylamine. The corresponding bromides 2 were obtained when carbon tetrabromide was used instead of carbon tetrachloride. Imidoyl iodides 3 were prepared by substitution of the chloro group of 1 by iodide ion in acetone

Synthesis of enantiomerically pure binaphthyl derivatives. Mechanism of the enantioselective, oxidative coupling of naphthols and designing a catalytic cycle

Abstract: Three different mechanisms have been identified for the CuCl 2 -mediated oxidative coupling of naphthols to binaphthyls in the presence of chiral amines (sparteine or α-methylbenzylamine); fair to excellent enantioselection has been observed (up to 100 % ee). The choice of the dominant mechanism appears to be critically dependent on the structure of the partners to be coupled. Thus, for the self-coupling of 2-naphthol (1) the enantioselection is mainly controlled of via a second-order asymmetric transformation of the product 4 (up to 100 % ee). The same mechanism is responsible for the formation of enantiomerically enriched biphenanthrol 9 (76% ee). By contrast, enantiodifferentiation in the formation of 5 and 7 results from the diastereoselective crystallization of the corresponding Cu(II)-amine-binaphtyl complex, wheras an enantioselective coupling operates in the preparation of 6. A catalytic cycle has been designed, employing 10 mol% of CuCl 2 (with AgCl to regenerate Cu II ) and sparteine(20 mol%); when applied to the asymmetric cross-coupling 1+3→6, the product (-)6 was obtained in 41%yield

A new synthesis of highly functionalized oxazoles

Abstract: Functionalized oxazoles and bis-oxazoles are obtained by side-chain oxidation of β-hydroxy amides with the Dess-Martin periodinane, followed by cyclodehydration with triphenylphosphine/iodine in the presence of triethylamine

Site-selective fluorination of organic compounds using 1-alkyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane salts (selectfluor reagents)

Abstract: The new «N-F»-type electrophilic reagent family of 1-alkyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane salts 8d (derived from elemental fluorine (F 2 ) and 1-alkyl-1,4-diazabicyclo[2.2.2]octane salts) has been found to be very effective for the fluorination of a wide variety of organic substrates. These include steroidal enol acetates and silyl enol ethers, phenyl-substituted olefins, sulfides bearing α-H atoms, certain carbanions, and mildly activated aromatic compounds. The products were obtained with good yields and regioselectivity under very mild reaction conditions

Palladium-catalyzed coupling of arylstannanes with organic sulfonates : a comprehensive study

Abstract: The effect of ligands and lithium chloride on the rates of the palladium catalyzed coupling between organic triflates and arylstannanes was studied. The dependence of the rate on the ligand is similar to the one previously reported for the coupling of vinylstannanes, but in the present case triphenylarsine is shown to be superior to both triphenylphosphine and tri(2-furyl)phosphine. The effect of added chloride is compler and varies depending on solvent and ligand used. Ortho-substituted arylstannanes tend to transfer alkyl moieties to a substantial extent, and therefore rates and efficiencies of aryl vs alkyl transfer were quantitated

.alpha.-Lithioamine synthetic equivalents: syntheses of diastereoisomers from Boc derivatives of cyclic amines

Abstract: Sequences of α'-lithiations and electrophilic substitutions of Boc-pyrrolidines, Boc-piperidines, and Boc-hexahydroazepines that provide compounds which are substituted adjacent to nitrogen are reported, and the pathways of the reactions are discussed. By this methodology monosubstituted 2 and disubstituted 2,4, 2,6, and 2,5 Boc-piperidines are obtained as single or separable diastereoisomers consistent with equatorial lithiations and retentive electrophilic substitution in chair conformations

Catalytic asymmetric oxidation of sulfides to sulfoxides with tert-butyl hydroperoxide using binaphthol as a chiral auxiliary

Abstract: The asymmetric oxidation of sulfides chiral sulfoxides in moderate yield with tert-butyl hydroperoxide (TBHP) was catalyzed very effectively by a titanium complex produced in situ from a titanium alkoxide and a chiral binaphthol. The highest enantioselectivities (up to 96 % ee) were obtained with commercial aqueous 70% TBHP under atmospheric conditions at 25 oC with 2.5 mol % of the catalyst. The presence of more than 1.0 mol equiv of water relative to sulfide was essential for the oxidation, and it was found that the water was necessary not only to produce an effective catalyst for the highly enantioselective oxidation but also to maintain the catalytic activity of the titanium-binaphthol complex for a longer time. The nature of the solvent had a remarkable effect upon the ee of the sulfoxide. Carbon tetrachloride was proven to be the solvent of choice; the use of other chlorinated solvents resulted in low enantioselectivity. A moderate level of asymmetric amplification was observed in this catalytic system. From a mechanistic standpoint, it was revealed that the initial asymmetric oxidation to the chiral sulfoxide is followed by the kinetic resolution of the sulfoxide; that is, the titanium-binaphtol complex catalyzes not only the asymmetric oxidation but also the subsequent kinetic resolution

Total synthesis of 1233A

Abstract: The total synthesis of the HMG-CoA synthase inhibitor 1233A (1), starting from either (R)-pulegone (6) or diketo ester 12, is described. The key transformations included the diastereoselective [2,3] rearrangements of allylic ethers 9 and 19 to alcohols 10 and 11b, respectively, and the diastereoselective hydroboration of 11b to form 19. A Pd-mediated coupling of iodo olefin 31a with tert-butyl crotonate under newly devised conditions provides an efficient preparation of the diene portion of 1233A

Biomimetic synthesis of (.+-.)-crambines A, B, C1, and C2. Revision of the structure of crambines B and C1

Abstract: Crambines A (7) (eight steps, 22%). B (45d) (eight steps, 19%), C1 (98) (seven steps, 21%), and C2 (9a) (seven steps, 27%) have been synthesized expediently and stereospecifically by a biomimetic route from methyl acetoacetate. Aminodihydropyrimidines 39 and 40 are formed efficiently from enone ester 36 by a two-step procedure involving addition of O-methylisourea to give methoxydihydropyrimidine 37 followed by displacement of the methoxy group of 37 with ammonia. Hydrogenolysis of 40a and 40d afford crambines C2 and C1, respectively. Mesylation of the alcohol of 39a or 40a followed by Et 3 N-catalyzed cyclization and hydrogenolysis affords crambine A (7)

Improved enantioselectivity in asymmetric dihydroxylations of terminal olefins using pyrimidine ligands

Abstract: Bis-cinchona alkaloid substituted pyrimidine ligands were found to give improved enatioselectivity in the osmium-catalyzed symmetric dihydroxylation (AD) of monosubstituted terminal olefins

Recognition sites incorporating both pyridinyl and carboxy functionalities prepared by molecular imprinting

Abstract: Noncovalent molecular imprinting using simultaneously two chemically distinct functional monomers, namely the weedy basic 2-vinylpyridine and the acidic and hydrogen bonding methacrylic acid, war demonstrated in ethylene glyool dimethacrylate bared copolymers. Terpolymerizations of this type were shown to be particularly useful for the preparation of imprints against carboxylic acids, which additionally contained a complex array of other chemical functionalities. Such imprinted polymers demonstrated improved recognition capabilities as compared with polymers which were prepared using only one of the functional monomers

A practical process for the preparation of tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborole-borane. A highly enantioselective stoichiometric and catalytic reducing agent

Abstract: A practical, large-scale process for the preparation of tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo-[1,2-c] [1,3,2] oxazaborole-borane is reported. The title compound is a stable, free-flowing crystalline solid useful either stoichiometrically or catalytically for the enantioselective reduction of prochiral ketones. When used stoichiometrically to reduce acetophenone the enantioselectivity is ≥99.8% ee