Lewis acid catalyzed reaction of arylvinylidenecyclopropanes with acetals: a facile synthetic protocol for the preparation of indene derivatives

[Structure: see text] A number of highly substituted indene derivatives have been prepared in good yields by the reactions of arylvinylidenecyclopropanes 1 with acetals 2 in the presence of Lewis acid under mild conditions. The reaction is believed to proceed via regioselective addition of oxonium intermediate to arylvinylidenecyclopropane and the subsequent intramolecular Friedel-Crafts reaction.     

A phosphorimidate rearrangement for the facile and selective preparation of allylic amines

Allylic phosphorimidates, readily prepared from the combination of an allylic alcohol, an azide, and a chlorophosphite, undergo [3,3]-rearrangement under thermal conditions to provide single isomers of allylic phosphoramidates. This new rearrangement is tolerant of a range of substitution patterns on the reactants. Treatment of the products of the rearrangement with ethanethiolate followed by acid produces a protected allylic amine. This strategy thus provides an attractive and versatile procedure for the preparation of key synthetic intermediates, allylic amines.     

Lewis acid-mediated Michaelis-Arbuzov reaction at room temperature: a facile preparation of arylmethyl/heteroarylmethyl phosphonates

A facile preparation of arylmethyl and heteroarylmethyl phosphonate esters was achieved involving a Lewis acid mediated Michaelis-Arbuzov reaction at room temperature. Interaction of arylmethyl halides/alcohols with triethyl phosphite in the presence of Lewis acid at room temperature afforded phosphonate esters in good yields.     

Lewis acid-mediated cycloaddition of methylenecyclopropanes with aldehydes and imines: a facile access to indene, THF, and pyrrolidine skeletons via homoallylic rearrangement protocol

Methylenecyclopropanes (MCPs) 1 can react with aldehydes and aldimines to give the corresponding indene, THF, and pyrrolidine cycloaddition products in the presence of BF(3).OEt(2) under mild reaction conditions.     

Lewis Acid catalyzed reactions of vinylidenecyclopropanes with activated carbon-oxygen double bond: a facile synthetic protocol for functionalized tetrahydrofuran and 3,6-dihydropyran derivatives

A number of functionalized tetrahydrofuran and 3,6-dihydropyran derivatives are prepared selectively in moderate to good yields by the reactions of vinylidenecyclopropanes with activated carbonyl compounds in the presence of Lewis acid.     

Cobalt-catalyzed one-pot three-component coupling route to beta-acetamido carbonyl compounds: a general synthetic protocol for gamma-lactams

An efficient improved procedure for the synthesis of beta-acetamido carbonyl compounds is developed by a cobalt(II) chloride-catalyzed three-component coupling protocol. The procedure is also amenable to the synthesis of gamma-lactams by a three-component coupling reaction with use of 2-carbomethoxybenzaldehyde. The beta-acetamido carbonyl compounds derived from 2-carbomethoxybenzaldehyde are useful intermediates as they can be transformed to the corresponding gamma-lactams on treatment with base.     

Mannich-type reaction with trifluoromethylated N,O-hemiacetal: facile preparation of beta-amino-beta-trifluoromethyl carbonyl compounds

On treatment of silyl enolates and an N,O-hemiacetal, derived from trifluoroacetaldehyde ethyl hemiacetal and p-anisidine, with GaCl(3) (0.2 equiv) and C(6)H(5)COCl (0.2 equiv) in propionitrile, Mannich-type reaction took place smoothly to afford beta-amino-beta-trifluoromethyl carbonyl compounds in high yields.     

Direct Leuckart-type reductive amination of aldehydes and ketones: a facile one-pot protocol for the preparation of secondary and tertiary amines

A high-yielding and facile one-pot Leuckart-type reaction for rapid access to a number of 2° and 3° amines is described.     

Lewis acid promoted highly stereoselective rearrangement of 2,3-aziridino alcohols: a new efficient approach to beta-amino carbonyl compounds

A new Lewis acid promoted rearrangement reaction of 2,3-aziridino alcohols was discovered, which involved the highly stereoselective construction of a diastereogenic quaternary carbon center and efficient formation of beta-amino carbonyl compounds in excellent yields. A wide variety of Lewis acids were proved to be effective for the reaction, and a possible reaction mechanism was also discussed.     

Reactions of 2,2-dihydropolyfluoroalkylaldehydes with amines: a facile synthetic method for fluoroalkyl enaminoketones

Reactions of 2,2-dihydropolyfluoroalkylaldehydes (1) with amines (2) were studied. Both aliphatic amines and electron-deficient aromatic amines readily reacted with 1 in acetonitrile and water under reflux to give fluoroalkyl enaminoketones (3) in high yields, while no condensed products were obtained by reactions of 1 with electron-rich aromatic amines under similar conditions. In the presence of triethylamine, however, the reaction of 1 with electron-rich aromatic amines at room temperature gave 3 in low yields.     

Lewis acid mediated reactions of 1-cyclopropyl-2-arylethanones with allenic esters: a facile synthetic protocol for the preparation of dihydrofuro[2,3-h]chromen-2-one derivatives

TMSOTf-mediated reactions of 1-cyclopropyl-2-arylethanones with allenic esters afford a novel method for the synthesis of dihydrofuro[2,3-h]chromen-2-one derivatives in moderate to good yields. This process is a sequential reaction involving a nucleophilic ring-opening reaction of the cyclopropane by H(2)O, two intermolecular aldol-type reactions and one intramolecular aldol-type reaction, a cyclic transesterification, dehydration, and aromatization mediated by Lewis acid.     

Polyethylene glycol mediated facile protocol for N-Cbz protection of amines

Abstract

We have reported an efficient and eco-friendly protocol for the protection of various structurally and electronically divergent aryl and aliphatic amines using Cbz-Cl in the presence of polyethylene glycol (PEG)-400 at room temperature. The reaction afforded excellent yields with low as well as high molecular weight PEGs.     

Lewis acid catalyzed reaction of arylvinylidenecyclopropanes with ethyl (arylimino)acetates: a facile synthetic protocol for pyrrolidine and 1,2,3,4-tetrahydroquinoline derivatives

[reaction: see text] A number of pyrrolidine and 1,2,3,4-tetrahydroquinoline derivatives are prepared selectively in moderate to good yields by the reaction of arylvinylidenecyclopropanes 1 with ethyl (arylimino)acetates 2 in the presence of Lewis acid depending on the electronic nature both of 2 and R1 or R2 aromatic groups of 1.     

A facile protocol for N-Cbz protection of amines in PEG-600

正An efficient and eco-friendly protocol for the chemoselective N-benzyloxycarbonylation of amines was described.The reaction of amines with benzyl chloroformate(Cbz-Cl) in the presence of PEG-600 at room temperature afforded the corresponding N-Cbz derivatives in excellent yields.The method is applicable to the N-Cbz protection of aliphatic(acyclic and cyclic) and aromatic amines.     

Readily available (S)-proline-derived organocatalysts for the Lewis acid-mediated Lewis base-catalyzed stereoselective aldol reactions of activated thioesters

A set of enantiomerically pure Lewis bases containing different diphenyl phosphinyl oxide groups were easily synthesized in a straightforward procedure by reaction of readily available proline-based scaffolds and phosphinoyl chlorides. The newly synthesized derivatives were employed (0.1 mol equiv) as organocatalysts in the Lewis acid-mediated Lewis base-promoted direct stereoselective aldol reactions of activated thioesters with aromatic aldehydes, carried out in the presence of tetrachlorosilane and a tertiary amine. β-Hydroxy thioesters were obtained in moderate to high yields, with very high syn diastereoselectivities (dr up to >98:2), and fair enantioselectivities (ee up to 51%). Theoretical studies were performed in order to elucidate the origin of the stereoselection.     

Chiral recognition in cyclic alpha-hydroxy carbonyl compounds: a theoretical study

A theoretical study (DFT and MP2) of the self-association of homochiral (RR or SS) and heterochiral (RS or SR) dimers of three series of cyclic alpha-hydroxy-carbonyl derivatives has been carried out. The solvation effect on the parent derivative dimers has been explored, showing nonsignificant changes in the configurations preferred but altering in some cases the homo/heterochiral preference of the dimers. The results in the gas phase of the systems with different substituents show a preference for the heterochiral dimers. The energetic results have been analyzed with the NBO and AIM methodologies. Optical rotatory power calculations of the monomers and homochiral dimers show large variations of this parameter depending on the substituents and the complexation.     

A novel hydride-mediated reductive rearrangement of amide: a facile synthesis of pyrimidyl and triazinyl amines

LiAlH₄ and NaBH₄ were found to mediate the conversion of 2-(pyrimidyl-2-ylsulfanyl)-N-arylbenzamides and 2-(triazinyl-2-ylsulfanyl)-N-arylbenzamides into pyrimidyl and triazinyl amines under notably mild conditions via a novel reductive rearrangement mechanism. These reactions invent a new route to prepare amines, which are a kind of important biologically active compounds and provide the first insight into a novel hydride-promoted reductive rearrangement of amides.     

Zinc-mediated alkynylation of carbonyl compounds with iodoalkynes: a facile synthesis of propargyl alcohols

A straightforward synthesis of propargyl alcohols from alkynyl iodides and carbonyl compounds using zinc is described.     

A greener synthetic protocol for the preparation of carbodiimide

A new and facile preparation of symmetrical and unsymmetrical 1,3-diaryl and aryl-alkyl carbodiimides via a dehydrosulfurisation of their corresponding thioureas is described. Herein, the classical method of oxidative desulfurisation of thiourea to carbodiimide involving toxic heavy metal oxides (HgO) has been replaced with an easily available, cost-effective and environmentally benign reagent, iodine. Simple reaction conditions, easy purification of the products and high yields are important attributes of the present methodology and perhaps the best alternative from a green chemistry perspective. The only limitation to this method however, is in the preparation of 1,3-dialkyl substituted carbodiimide.