Convenient Stereoselective Synthesis Research Articles

Convenient stereoselective synthesis of some 3-aminosteroid scaffolds

An efficient stereoselective synthesis 3α- and 3β-aminoandrostan-17-one and 3α-amino dehydroepiandrosten-17-one based on a Mitsunobu reaction has been developed, using azide as the ammonia equivalent. All the products were isolated in high yield.

Microwave Induced Stereoselective Synthesis of O–Vinyl Oximes using Acetylenic Esters as Efficient Michael Acceptors

AbstractA new and convenient stereoselective synthesis of O–vinyl oximes involving Michael addition of N–hydroxysuccinimidyl derivatives to dialkyl acetylenedicarboxylates under conventional and microwave irradiation methods is described. Michael acceptors diethyl and dimethyl acetylenedicarboxylates yielded a mixture of syn‐(E) and anti‐(Z) isomers by conventional method. However, microwave irradiation stereoselectively yielded both isomers at different experimental parameters. The role of lone pairs of oxygen in sp3‐hybridized state in controlling the conformational preferences about N−O bond has also been demonstrated. The structures and stereochemistry of the adducts were established through FT‐IR, 1H, 13C NMR spectroscopy and X–ray crystallography.

A convenient stereoselective synthesis of 5-hydroxy-3-oxoesters and 3-hydroxy-5-oxoesters

A biocatalytic approach was employed for the asymmetric reduction of sterically demanding ketones to prepare 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates. Screening a collection of microorganisms led to the identification of stereocomplementary microbial strains that provide access to both enantiomers of 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates with high enantiomeric excess (up to 99% ee). Moreover, the application of Saccharomyces cerevisiae gave two diastereomers of 3,5-dihydroxy-5-phenylpentanoates with high enantiomeric excess (up to 99% ee). The applicability of the identified strains was demonstrated by transforming the obtained dihydroxy ester into the chemically valuable lactone (4S,6R)-tetrahydro-4-hydroxy-6-phenyl-pyran-2-one.

ChemInform Abstract: Convenient Stereoselective Synthesis of β‐Perfluoroalkyl α,β‐Unsaturated Esters via Horner—Wadsworth—Emmons Reactions.

AbstractVarious title esters are obtained with high (E)‐stereoselectivity by condensation reactions of in situ produced halogenated ketones with Horner—Wadsworth—Emmons reagents.

Convenient stereoselective synthesis of β-perfluoroalkyl α,β-unsaturated esters via Hörner–Wadsworth–Emmons reactions

Condensation of Hörner–Wadsworth–Emmons reagents 3 and ketones 2 with a perfluoroalkyl (Rf) moiety prepared in situ was proved to be significantly efficient and powerful methods for the construction of a wide variety of α,β-unsaturated esters with Rf and R1 groups both at the β-position due to convenient avoidance of usually tedious as well as troublesome isolation steps of these ketones 2.

Convenient Stereoselective Synthesis of Substituted Ureido Glycosides Using Stable 4-Chlorophenylcarbamates without the Requirement of Lewis Acids

A modification of the synthesis of substituted ureido glycosides in a stereospecific fashion is described, in which commercially available azido glycosides are reduced to the amines, which are then reacted with 4-chlorophenyl chloroformate to the corresponding 4-chlorophenyl carbamate of the glycosides. These synthetic intermediates are stable at room temperature and have a long shelf life, and can transiently form the 1-isocyanato glycosides under mildly basic conditions, which subsequently can react with amines to form substituted ureido glycosides

ChemInform Abstract: A Convenient Stereoselective Synthesis of trans‐4a,5,8,8a‐Tetrahydro‐2H‐isoquinolin‐1‐ones via trans 3‐Allylation of 4‐Allyl‐3,4‐dihydropyridine‐2‐thiones and RCM as Key Steps.

AbstractThe process offers a convenient access to the desired heterocyclic skeleton, present in alkaloids and synthetic drugs.

ChemInform Abstract: A Convenient Stereoselective Synthesis of Conjugated 2Z-En-4-ynoic and 2Z,4Z- and 2Z,4E-Dienoic Acid Derivatives from Propiolic Acid Derivatives.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: A Convenient Stereoselective Synthesis of Fluorinated α- Alkylidene-γ-butyrolactone Derivatives.

Abstract Fluorinated α-alkylidene-γ-butyrolactone derivatives were synthesized stereoselectively via a sodium dithionite initiated radical perfluoroalkylation-cyclization of acyclic allylic alkynoates in high yields under mild conditions.

A Convenient Stereoselective Synthesis of trans-4a,5,8,8a-Tetrahydro-2H-isoquinolin-1-ones via trans 3-Allylation of 4-Allyl-3,4-dihydropyridine-2-thiones and RCM as Key Steps

A convenient synthesis of trans-4a,5,8,8a-tetrahydro-2H-isoquinolin-1-ones from 4-allyl-3,4-dihydro-1H-pyridine-2-thiones via stereoselective alkylation at C-3 (trans with respect to 4-allyl substituent), subsequent N-alkylation (optionally for NH derivatives) followed by ring-closing metathesis (RCM) of corresponding trans-3,4-diallyl-3,4-dihydro-1H-pyridine-2-ones is described. The high synthetic potential of the obtained bicyclic pi­peridinones, exemplified by the synthesis of threecyclic [1,3]oxazino[3,2-b]isoquinolin-6-one via N-acyliminum cation, is presented.

A Mild and Efficient Method for Chlorination of Baylis–Hillman Adducts Using PPh3/Cl3CCONH2

AbstractA new and convenient stereoselective synthesis of (Z)‐2‐(chloromethyl)alk‐2‐enoates has been achieved from Baylis–Hillman adducts by treatment with PPh3/Cl3CCONH2 at room temperature. The synthesis can proceed under mild and acid‐free conditions to form the products in high yields.

Chiral 1,3,6‐Trisubstituted 2,4‐Dioxohexahydropyrimidines: A Convenient Stereoselective Synthesis from Aspartic Acid Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Chiral 1,3,6-trisubstituted 2,4-dioxohexahydropyrimidines: a convenient stereoselective synthesis from aspartic acid derivatives

Chiral 1,3,6-trisubstituted 2,4-dioxohexahydropyrimidines were easily synthesized by reaction of homoaspartic acid derivatives with isocyanates, followed by cyclization of the resulting urea, and alkylation at N1 position.

Convenient Stereoselective Synthesis of (Z)‐Chalcone Derivatives from 1,3‐Diaryl‐2‐propynyl Silyl Ethers.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Convenient stereoselective synthesis of ( Z)-chalcone derivatives from 1,3-diaryl-2-propynyl silyl ethers

Various ( Z)-chalcone derivatives were easily synthesized in a stereoselective manner from 1,3-diaryl-2-propynyl silyl ethers by a catalytic reaction using potassium tert-butoxide under very mild conditions after acid treatment.

Synthesis of Functionalized Homoallylsilanes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Convenient Stereoselective Synthesis of 3‐Hydroxy‐2‐iodo‐2(E)‐Alkenyl Sulfides via Iodohydroxylation of 1,2‐Allenyl Sulfoxides in the Presence of BnSH.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Convenient stereoselective synthesis of 3-hydroxy-2-iodo-2( E)-alkenyl sulfides via iodohydroxylation of 1,2-allenyl sulfoxides in the presence of BnSH

The iodohydroxylation of 1,2-allenyl sulfoxides with I 2 in the presence of BnSH affords 3-hydroxy-2-iodo-2( E)-alkenyl sulfides in good yields and selectivities. The stereochemistry for the products of this transformation is opposite to what was obtained from the iodohydroxylation of 1,2-allenyl sulfides. Based on the results of some control experiment, a mechanism was proposed.

A Convenient Stereoselective Synthesis of β‐Lactams from β‐Hydroxy‐α‐thioalkylesters Prepared from Michael/Aldol Tandem Reaction or Stereoselective Addition of Thiols to the Baylis—Hillman Adducts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of Functionalized Homoallylsilanes

A convenient stereoselective synthesis of functional homoallylsilanes 2 has been developed by reaction of trimethylsilanylmethylmagnesium chloride on the Baylis–Hillman acetates 1, in anhydrous tetrahydrofuran (THF) in the presence of a catalytic amount of LiCuBr2.