Govindasamy Sekar

General, Mild, and Intermolecular Ullmann-Type Synthesis of Diaryl and Alkyl Aryl Ethers Catalyzed by Diol−Copper(I) Complex†

A wide range of diaryl ethers and alkyl aryl ethers are synthesized through intermolecular C(aryl)-O bond formation from the corresponding aryl iodides/aryl bromides and phenols/alcohols through Ullmann-type coupling reaction in the presence of a catalytic amount of easily available (+/-)-diol L3-CuI complex under very mild reaction conditions. Less reactive aryl bromides can also be used for O-arylation of phenols under the same reaction conditions without increasing the reaction temperature, catalyst loading, and time. The catalytic system not only is capable of coupling hindered substrate but also tolerates a broad range of a series of functional groups.

An efficient method for the cleavage of aziridines using hydroxyl compounds

Abstract A variety of N-activated aziridines were opened with water, primary, allylic, and propargyl alcohols at rt in high yield using a catalytic amount of Sn(OTf)2 or BF3·OEt2.

An efficient method for opening nonactivated aziridines with TMS azide: application in the synthesis of chiral 1,2-diaminocyclohexane ☆

A variety of N-substituted aziridines have been opened with TMS azide in MeCN at rt in the absence of any Lewis acid. The reaction was extended to the synthesis of (R,R)- and (S,S)-1,2-diaminocyclohexane.

Cu(OTf)2 - DBN/DBU complex as an efficient catalyst for allylic oxidation of olefins with tert-butyl perbenzoate

Abstract Olefins, on treatment with tert -butyl perbenzoate in the presence of a catalytic amount of a complex of Cu(OTf) 2 and chelating ligands such as DBN and DBU gave allylic benzoates under milder conditions. A variety of olefins were tested in the reaction.

Enantiomerically pure N-aryl-β-amino alcohols by enzymatic resolution

N-Aryl-β-amino acetates, obtained by opening epoxides with aromatic amines followed by acetylation of the hydroxyl group, were resolved using crude pig liver esterase (PLE) enzyme in DMSO in high enantiomeric excess.

Domino Synthesis of Thiochromenes through Cu-Catalyzed Incorporation of Sulfur Using Xanthate Surrogate

An efficient domino reaction has been developed for the synthesis of thiochromenes through Cu-catalyzed in situ incorporation of sulfur. This domino method avoids the use of less accessible and unpleasant arenethiols as starting materials, instead utilizes very stable aryl halides along with potassium ethyl xanthate as an odorless sulfur surrogate. The domino methodology proceeds through C(aryl)-S coupling, thioester cleavage, sulfa-Michael addition, aldol reaction, and elimination reaction sequences to provide thiochromenes in good yields.

NIS Mediated Cross-Coupling of C(sp2)–H and N–H Bonds: A Transition-Metal-Free Approach toward Indolo[1,2-a]quinazolinones

A metal- and base-free protocol for intramolecular cross-coupling of C(sp2)-H and N-H bonds using N-iodosuccinimide (NIS) has been demonstrated. This environmentally benign approach furnishes a series of substituted indolo[1,2-a]quinazolinones from the suitably fabricated indoles via C-N bond forming cyclization in 28-82% yield. A plausible mechanism is proposed for this cyclization based on the results of a control experiment. This methodology requires no additional metal catalyst, oxidant, or base. Furthermore, the synthetic utility of the protocol is demonstrated by performing a gram scale reaction.