Showing papers on "Intramolecular reaction published in 1994"
113 citations
TL;DR: A pentacyclic compound was synthesized as an important intermediate of antitumor antibiotic dynemicins as discussed by the authors, using the Heck reaction using catalytic Pd reagent, and an unusual spiro ring compound was found to be produced via intramolecular conjugate addition.
109 citations
TL;DR: The intramolecular [4+2] cycloaddition of conjugated enynes provides an efficient and general route to aromatic and dihydroaromatic compounds.
Abstract: The intramolecular [4+2] cycloaddition of conjugated enynes provides an efficient and general route to aromatic and dihydroaromatic compounds
105 citations
84 citations
TL;DR: In this article, a trans-fused medium-size cy-clic ethers were constructed using intramolecular oxirane ring expansion in cycloalkenes to give bridged oxabicyclic systems.
Abstract: A successful design for the construction of trans-fused medium-size cy- clic ethers is described. The key features of the synthesis are as fol- lows: (i) intramolecular oxirane ring expansion in cycloalkenes to give bridged oxabicyclic systems and (ii) linear, one- or two-directional synthetic operations which generate external oxocycles in single reac- tion steps. The general approach involves the intramolecular addition of a stable γ-alkoxy-substituted allylstannane to an aldehyde carbonyl group, and the entire reaction is conducted in a one-pot process which includes the following: (i) vic-diol fragmentation from the bridged oxabicyclic precursor and (ii) Lewis acid-induced cyclization of the resulting aldehyde-allylic tin system. While the present strategy was mostly developed around racemic models, the potential for adoption of enantioselective features is immediate. The versatility, scope, limi- tations, and potential applications of the present technology are discussed in detail
83 citations
TL;DR: In this article, a non-carbohydrate-based enanti-lective approach to (-)-swainsoni-ne (1) is described, in which the aqueous intramolecular Diels-Alder reaction of a chiral acylnitroso diene has been employed as a key reac- tion.
Abstract: A new noncarbohydrate-based enantioselective approach to (-)-swainsoni- ne (1) is described, in which the aqueous intramolecular Diels-Alder reaction of a chiral acylnitroso diene has been employed as a key reac- tion. The intramolecular cycloaddition of the chiral hydroxamic acid (9), available from D-malic acid in (10) steps, with Pr 4 NIO 4 was con- ducted under the conventional nonaqueous conditions using CHCl 3 as a solvent, where upon intermediacy acylnitroso compound (10) cyclized spontaneously to give the trans- and cis-1,2-oxazinolactams (11) and (12) with a low diastereoselction of 1.3:1 in 76% combined yield. When the corresponding reaction was performed in water, it led to signifi- cant enhancements of trans selectivity of 4.1:1 as well as combined yield (89%). The trans adduct (11) was subjected to reductive N-O bond cleavage followed by diastereoselective hydroxylation with OsO 4 to provide the 1,2-glycol (21), which was then converted to the amino alcohol (25). Intramolecular cyclodehydration of (25) with CBr 4 /PPh 3 - /Et 3 N and subsequent deprotection furnished (-)swainsonine
76 citations
TL;DR: A lithiation-intramolecular cyclization reaction of N-Boc chloroalkyl secondary amines is reported to provide the 2-aryl-substituted pyrrolidine and piperidines (6), (7), (9), and (11) and a series of 2-azabicyclo[3.1.0] derivatives as discussed by the authors.
Abstract: A lithiation-intramolecular cyclization reaction of N-Boc chloroalkyl secondary amines is reported to provide the 2-aryl-substituted pyrrolidine and piperidines (6), (7), (9), and (11) and a series of 2-azabicyclo[3.1.0] derivatives (14-25), including cyclopropane derivatives of proline and of the indolizidine-pyrrolizidine alkaloid ring system. Lithiation-substitutions of N-Boc-N-ethylcyclopropylamine to give (27-29) and lithiation-silylations of N-Boc aziridines to give (31-33) also are reported
74 citations
TL;DR: A series of alkenyl-substituted imides were prepared by treating the appropriate amide with 2,2,6-trimethyl-4H-1,3-dioxen-4-one in xylene at 140 o C to give the N-acetoacylated imides.
Abstract: A series of alkenyl-substituted imides were prepared by treating the appropriate amide with 2,2,6-trimethyl-4H-1,3-dioxen-4-one in xylene at 140 o C to give the N-acetoacylated imides. Exposure of these imides to standard diazo transfer conditions gave the desired diazoimides. The carbenoid intermediate derived by treatment of the diazoimide with rho- dium(II) acetate undergoes ready cyclization onto the neighboring amide carbonyl oxygen atom to generate an isomunchnone intermediate. Subse- quent 1,3-dipolar cycloaddition across the pendant olefin affords the cycloadduct in high yield. The stereochemical assignment of several of the cycloadducts was deduced by X-ray crystallography. The stereochemi- cal outcome of the reaction is the consequence of an endo cycloaddition of the neighboring π-bond across the transient isomunchnone dipole. Mo- lecular mechanics calculations were used to model energy differences between the endo and exo diastereoisomers. The calculations reveal that the endo diastereomers are significantly (8-12 kcal/mol) lower in energy than the correspnding exo isomers thereby providing a rationale for the preferred endo cycloaddition
70 citations
TL;DR: A variety of substituted 2-cyclopentenones are obtained in good yields via intramolecular 1,5-carbon-hydrogen insertion reactions of [β-(p-toluenesulfonyl)alkylidene]carbenes derived from Michael addition of sodium p-tolieneullanate to β-ketoethynyl(phenyl)iodonium triflates.
Abstract: A variety of substituted 2-cyclopentenones are obtained in good yields (53-82%) via intramolecular 1,5-carbon-hydrogen insertion reactions of [β-(p-toluenesulfonyl)alkylidene]carbenes derived from Michael addition of sodium p-toluenesullanate to β-ketoethynyl(phenyl)iodonium triflates. An extension of the methodology using β-amidoethynyl(phenyl)iodonium triflates provides a facile synthesis of γ-lactams including fused bicyclic systems. The isomerization of a substituted cyclopentenone on silica gel is also reported
70 citations
TL;DR: Furans containing a functional group at C(5) were obtained under neutral conditions by selective cyclization of (Z)-pent-2-en-4-yn-1-ols in the presence of RuCl2(PPh3)(p-cymene) as catalyst precursor as discussed by the authors.
Abstract: Furans containing a functional group at C(5) are obtained under neutral conditions by selective cyclization of (Z)-pent-2-en-4-yn-1-ols in the presence of RuCl2(PPh3)(p-cymene) as catalyst precursor.
68 citations
TL;DR: Generation of an intramolecularly tethered, nonracemic diaryl cuprate followed by its oxidation with ground state oxygen at −78° leads to a biaryl precursor to an ellagitannin this paper.
TL;DR: Sulfenamides are synthesised from reaction between amines and N -(benzenesulfenyl)-phthalimide or benzenes sulfenyl chloride.
TL;DR: Asymmetric inductions up to 71% have been observed in a Pd catalyzed version of an intramolecular Alder ene reaction as discussed by the authors, where the inductions were obtained in the case of Pd-catalyst Alder Ene reactions.
TL;DR: In this paper, a 2,6-dialkylated piperidine was converted into the title alkaloids in an S N 2′ mode in the presence of a Pd(O) catalyst and n -Bu 4 NI.
TL;DR: The palladium-catalyzed coupling of vinylic halides and olefinic sulfonamides affords good yields of 2-(1-alkenyl)pyrrolidine and -piperidine sulfon amides via vinylpalladium addition to the oleinfin, regioselective rearrangement to a π-allylpalladium intermediate, and subsequent intramolecular nucleophilic displacement of palladium as discussed by the authors.
Abstract: The palladium-catalyzed coupling of vinylic halides and olefinic sulfonamides affords good yields of 2-(1-alkenyl)pyrrolidine and -piperidine sulfonamides via vinylpalladium addition to the olefin, regioselective rearrangement to a π-allylpalladium intermediate, and subsequent intramolecular nucleophilic displacement of palladium
TL;DR: In this article, the photochemical and photophysical behavior of several (N, N-dimethylamino)alkyl)styrenes in which the amino group is attached to the styrene α- or β-carbon by a methyl, ethyl, propyl, or butyl polymethylene chain has been investigated.
Abstract: The photochemical and photophysical behavior of several ((N,N-dimethylamino)alkyl)styrenes in which the amino group is attached to the styrene α- or β-carbon by a methyl, ethyl, propyl, or butyl polymethylene chain has been investigated. Efficient intramolecular addition of an aminomethyl C-H to styrene is observed in nonpolar. solvents for the (aminoethyl)styrenes, and addition of an aminomethylene C-H is observed for the (aminobutyl)styrenes. However, the (aminomethyl)- and (aminopropyl)styrenes do not undergo intramolecular addition reactions. Both the reactive and unreactive (aminoalkyl)styrenes form fluorescent singlet exciplexes in nonpolar and polar solvents
TL;DR: In this paper, the pseudopterane and furanocembrane systems were obtained in 64% yield upon treatment of the 12-membered β-alkynyl allylic alcohol 14 with KO-t-Bu and 18-c-6 in THF t-BuOH.
Abstract: The prototype pseudopterane and furanocembrane systems 15 and 26 were prepared through a «furan last» approach. The former was obtained in 64% yield upon treatment of the 12-membered β-alkynyl allylic alcohol 14 with KO-t-Bu and 18-c-6 in THF-t-BuOH. The latter was formed in 88% yield from the 14-membered γ-alkynyl allylic alcohol 25 under comparable conditions. The carbocyclic precursors to these allylic alcohols, 11 and 24, were secured through intramolecular Horner-Emmons condensation of keto phosphonates 10 and 23, respectively, under Masamune-Roush conditions
TL;DR: In this article, a slow addition of tributylstannane to sulphenylimines 2 gave the corresponding Δ1-pyrrolenines 5 by an intramolecular addition of the intermediate iminyl radical, a process which can be easily coupled to an intermolecular add to an electrophilic olefin.
TL;DR: In this paper, a new entry to the cyclic amino alcohols was proposed, where oxime ethers connected by a tether to aldehydes or ketones efficiently cyclize in a free radical cyclization mediated by tributyltin hydride.
TL;DR: In this paper, an intramolecular 2-azaallyl anion cycloaddition with a diene produced the 2,3,4,6,7,7a-hexahydroindole with complete control of relative stereochemistry.
Abstract: An intramolecular 2-azaallyl anion cycloaddition with a diene produced the 2,3,4,6,7,7a-hexahydroindole 33 with complete control of relative stereochemistry, thus providing the first example of the use of such a cycloaddition in an approach to a relatively complex target molecule. The 2-azaallyl anion was generated by tin-lithium exchange of the (2-azaallyl)stannane 32. The stannane was prepared by a convergent route using a Stille coupling of the vinyl bromide 14 with the vinylstannane 28, providing the diene 29. An unexpected isomerization occurred in the Stille coupling. Transformation of the cycloadduct 33 to the allylic methyl ethers 36 and 37 produced potential precursors of 6a-epiprecriwelline (4) and 6a-epipretazettine (3), respectively. The inability to carry out an oxidative desilylation thwarted the completion of the syntheses of these alkaloids
TL;DR: The simple and induced diastereoselectivity of the intramolecular hetero-Diels-Alder reaction of the alkylidene 1,3-dicarbonyl compounds 7a-e, obtained in situ by Knoevenagel condensation of the aldehydes 5a − e and dimethylbarbituric acid 6, was investigated experimentally and theoretically as discussed by the authors.
Abstract: The simple and induced diastereoselectivity of the intramolecular hetero-Diels-Alder reaction of the alkylidene 1,3-dicarbonyl compounds 7a-e, obtained in situ by Knoevenagel condensation of the aldehydes 5a-e and dimethylbarbituric acid 6, was investigated experimentally and theoretically. In all examples the selectivity is very high; thus the domino reaction of 5a and 6 gives nearly exclusively the trans-fused tricyclic dihydropyran 8 (trans/cis=98.8:1.2). In the similar reactions of the chiral aldehydes 5b-e and 6 the trans-cycloadducts 28, 33, 36, and 41 are the main products out of four possible diastereomers. The induced diastereoselectivity for the reaction of 5b and 5e with 6 is >99:1 and for the reaction of 5c and 5d with 6, 95.2:3.6 and 94.1:4.7, respectively. Semiempirical AM1 calculations have been used to locate the transition structures of the intramolecular hetero-Diels-Alder reaction of 7a. The results were employed to create new parameters for the MM2-type force-field to determine the transition structures of 7b-e. The obtained data were compared with the experimental results of the cycloadditions and showed an excellent agreement
TL;DR: In this article, 1-bromo-2-methyl-2propyl ether derivatives of alcohols were treated with Bu 3 SnH(D) to obtain 1,5-hydrogen abstraction reactions.
TL;DR: In this article, the stereochemical issues required for the total synthesis of dynemicin A (1) have been resolved by employing an intramolecular Diels-Alder reac- tion and a diastereoselective addition of a magnesioacetylide to a qui- noline under the influence of methyl chloroformate.
Abstract: The stereochemical issues required for a total synthesis of dynemicin A (1) have been resolved by employing an intramolecular Diels-Alder reac- tion and a diastereoselective addition of a magnesioacetylide to a qui- noline under the influence of methyl chloroformate
TL;DR: In this article, the Ferrier reaction was used to obtain (−)-Calystegine B2 from D-Glucose via Ferrier reactions followed by regiospecific ring enlargement of a polysubstituted cyclohexanone and intramolecular cyclisation of 4-aminocycloheptanone.
TL;DR: A cis-diaqua copper(II) complex has been shown to promote the transesterification of a phosphate diester with second-order dependence on the metal complex as discussed by the authors.
Abstract: A cis-diaqua copper(II) complex has been shown to promote the transesterification of a phosphate diester with second-order dependence on the metal complex.
TL;DR: In this paper, the 3-O-acyl-α-methyl-d -mannopyranosides were used to give inverted β-mannophyranoides, but the yields were limited by competing 1,5-hydrogen transfer reactions that gave isomeric α-glucopyranoide.
TL;DR: In this article, the cyclization of γ, δ-alkenylimines with bromine in dichloromethane gave instantaneous formation of cyclic iminium bromides, which were converted into either pyrrolidines or piperidines, depending upon the substitution pattern.