InBr3-catalyzed sulfonation of indoles: a facile synthesis of 3-sulfonyl indoles

Indoles react smoothly with sulfonyl chlorides in the presence of a catalytic amount of indium tribromide at ambient temperature to afford the corresponding 3-arylsulfonyl indole derivatives in high yields with high regioselectivity.     

Facile and convenient synthesis of functionalized propargylic alcohols and amines: an InBr3-Et3N reagent system promotes the alkynylation of aldehydes and N,O- or N,S-acetals

The use of a novel InBr₃-Et₃N reagent system to promote the alkynylation of not only a variety of aromatic/heterocyclic or bulky aliphatic aldehydes but also N,O- or N,S-acetals is described. The use of N-silyl-N,O-acetals and 1-alkynes could lead to the direct production of primary propargylic amines in good yields.     

Lewis acid promoted alkynylation of imines with terminal alkynes: simple, mild and efficient preparation of propargylic amines

A mild and efficient addition of terminal alkynes to imines in the presence of ZnCl₂, Et₃N and TMSCl gives propargylamines in good yields.     

FeCl3/PPh3-catalyzed Sonogashira coupling reaction of aryl iodides with terminal alkynes

Conditions for a FeCl₃/PPh₃-catalyzed and palladium-, copper-, amine free-Sonogashira coupling reaction of aryl halides with terminal alkynes are reported. The protocol was applicable to a wide variety of substituted aryl iodides and alkynes with different steric and electronic properties and gave excellent yields of the desired coupling products.     

InCl3-catalyzed efficient synthesis of spiro-perimidine derivatives

InCl₃ was found to be a mild and effective catalyst for the simple and efficient synthesis of spiro-perimidine derivatives by the reaction of naphthalene-1,8-diamine and active carbonyl compounds in water at room temperature. This protocol includes some important aspects like the use of water as a “green” reaction medium, good yielding of products and mild reaction conditions.     

InBr3-Et3N promoted alkynylation of aldehydes and N,O-acetals under mild conditions: facile and simple preparation of propargylic alcohols and amines

The use of a novel InBr₃-Et₃N reagent system to promote addition reactions of 1-alkynes not only with a variety of aromatic or bulky aliphatic aldehydes but also with N,O-acetals is described. The corresponding propargylic alcohols or amines are produced in good to excellent yields.     

InBr3-catalyzed stereoselective synthesis of trans-2,6-disubstituted 3,6-dihydro-2H-pyrans

A new method for the stereoselective synthesis of trans-2,6-disubstituted 3,6-dihydro-2H-pyrans with a variety of substitution patterns is described, involving Lewis acid induced tandem allylation or cyanation of δ-hydroxy-α,β-unsaturated aldehydes to produce dihydropyrans in good yields and with trans-selectivity. This method is very useful for the synthesis of trans-2,6-disubstituted dihydropyran ring-containing natural products such as laulimalide, scytophycin C and many others.     

InBr3-catalyzed three-component, one-pot synthesis of imidazo[1,2-a]pyridines

Indium(III) bromide has been used for the first time for the synthesis of imidazo[1,2-a]pyridines in a one-pot operation from 2-aminopyridine, aldehydes, and alkynes. InBr₃ was found to be more effective for the activation of both alkyne and imine derived from aryl aldehyde and 2-aminopyridine.     

InCl3-catalyzed four-component reaction: a novel synthesis of N-carbazolyl dihydropyridines

We have developed a simple, efficient, and environmentally benign microwave-assisted InCl₃-catalyzed synthesis of N-carbazolyldihydropyridines via a four-component reaction of 3-amino-9-ethylcarbazole, malononitrile, aromatic aldehydes, and acetylenic esters. The use of microwave heating allowed for reduced reaction times and resulted in higher yields. This four-component reaction is atom-efficient, high-yielding, and applicable to a wide variety of four-component reactions.     

InBr3-catalyzed annulations of cyclic 1,3-diketones with aryl propargyl alcohols: a novel synthesis of 2,4-diaryldihydropyrans

The cyclic 1,3-dicarbonyl compounds undergo smooth cyclization with aryl propargyl alcohols in the presence of 10 mol % indium tribromide in refluxing dichloroethane to produce 2,4-diarylpyran derivatives in good yields with high selectivity.     

Diastereoselective alkynylation of glucose-modified imines with terminal alkynes

The copper(I)-catalyzed enantioselective alkynylation of aldimines incorporating a 2,3,4,6-tetrakis-O-pivaloyl-d-glucopyranosyl (Piv₄Glc) chiral auxiliary with terminal alkynes is reported. The present system provides a versatile tool for the construction of optically active propargylamine derivatives. Good yields and enantiomeric excess values were achieved with an array of imines and biologically active, propargylamine derivatives.     

Copper-catalyzed oxidative alkynylation of diaryl imines with terminal alkynes: a facile synthesis of ynimines

An efficient copper-mediated method for the oxidative alkynylation of diaryl imines with terminal alkynes is reported. This reaction provides the first catalytic and general synthesis of ynimines and allows for an easy preparation of these useful building blocks. An improved copper-catalyzed oxidative dimerization of imines to azines and the synthesis of dienes and azadienes from ynimines are also described.     

Facile direct synthesis of unsymmetrical ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines using DABAL-Me3

A practical synthetic method for the direct synthesis of unsymmetrically substituted ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines is described. In this study, efficient direct conversion of the Alloc-, Cbz-, and Boc-carbamate compounds to ureas was achieved in the presence of DABAL-Me₃, an air stable and easily handled reagent. Using this reaction method, both protected aromatic and aliphatic amines were successfully transformed into various trisubstituted and tetrasubstituted ureas with high yields without side product. Our findings offer promising guidelines for direct preparation of useful ureas from N-Alloc-, N-Cbz-, and N-Boc-carbamates.     

Copper-free PdCl2/PPh3-catalyzed Sonogashira coupling reaction of aryl bromides with terminal alkynes in water

A simple, copper-free and efficient catalytic system for the Sonogashira coupling reaction of aryl bromides with terminal alkynes in pure water has been developed. The use of PdCl₂/PPh₃ in the presence of pyrrolidine allows the coupling reaction to proceed at 120 °C in moderate to excellent yields.     

PtCl4-catalyzed cyclization of N-acetyl-2-alkynylanilines: A mild and efficient synthesis of N-acetyl-2-substituted indoles

An efficient synthesis of N-acetyl-2-substituted indole derivatives via direct intramolecular hydroamination of N-acetyl-2-alkynylaniline derivatives was developed. The reaction could be applied to a wide range of substrates employing only 1–2?mol% of PtCl₄ as the catalyst to furnish the desired indole products in moderate to excellent yields. The current protocol is efficient, reliable and scalable, and could serve as an important tool for convenient and rapid access to this important class of N-heterocyclic skeleton from readily available substrates.     

Efficient iron/copper cocatalyzed alkynylation of aryl iodides with terminal alkynes

We developed a highly efficient and practical protocol for the coupling of terminal alkynes with aryl iodides that is catalyzed by inexpensive and environmentally benign Fe/Cu. A broad spectrum of substrates can participate in the process effectively to produce desired products in good yields. The versatility, generality, low cost, and environmental friendliness, in combination with exceptionally high reaction rates, render this method particularly attractive for industrial applications.     

FeBr3-catalyzed regioselective hydroxysulfenylation of N-allylsulfonamides with sulfonyl hydrazides

Regioselective hydroxysulfenylation of unactivated CC double bonds was reported. Using FeBr₃-bpy as the catalyst, Na₂S₂O₈ as the oxidant, and sulfonyl hydrazides as the sulfenyl sources, hydroxysulfenylation of unfunctionalized olefins proceeded readily, giving a variety of β-hydroxysulfides in moderate to good isolated yields.     

InCl3-catalyzed efficient one-pot synthesis of 2-pyrrolo-3′-yloxindoles

An InCl₃-catalyzed one-pot synthesis of 2-pyrrolo-3′-yloxindoles was achieved via three-component reaction of 3-phenacylideneoxindole, β-keto ester, and ammonium acetate at reflux by a sequential Michael addition followed by Paal-Knorr condensation.     

PPh3-catalyzed synthesis of multifunctional vinylesters from terminal alkynoates and aromatic aldehydes

A new four-component reaction involving two starting materials is described. The reaction of terminal alkynoates with aromatic aldehydes catalyzed by PPh₃ (50 mol %) in CH₂Cl₂ at reflux afforded multifunctional vinylesters in moderate yields. A plausible mechanism is proposed.