A Highly Diastereo- and Enantioselective Hg(II)-Catalyzed Cyclopropanation of Diazooxindoles and Alkenes

Abstract

It is reported for the first time that Hg(II) can catalyze the cyclopropanation of diazo reagents and alkenes, which contributes to the unprecedented highly diastereo- and enantioselective synthesis of spirocyclopropyloxindoles.

Mechanism and stereoselectivity of the Rh(ii)-catalyzed cyclopropanation of diazooxindole: a density functional theory study

“…[1][2][3][4] Therefore, spirocyclic oxindole scaffolds have continued to draw attention in recent years. [8][9][10][11][12] Since the pioneering work of Nozaki and Noyori, 13 the transition metal-catalyzed asymmetric cyclopropanation between diazo compounds and alkenes has emerged as a powerful strategy for the synthesis of cyclopropane derivatives. [5][6][7] As a result, great efforts have been directed toward asymmetric construction of these scaffolds.…”

Hg(OTf)2 Catalyzed Intramolecular 1,4-Addition of Donor–Acceptor Cyclopropenes to Arenes

“…4,5 The most relevant indicator for a mercury carbene in reactions of a diazo compound is that of mercury(II) catalyzed cyclo-propanation reactions of diazooxindoles which was reported in this journal by Zhou and co-workers. 5 We have recently described intramolecular C–H insertion reactions of N -benzyl-enoldiazoacetamides at the benzyl C–H bond to form β -lactams that occur in competition with the Buchner reaction at the aromatic ring of the benzyl group; 1a since these reactions occur in high yields with dirhodium(II), copper, and silver catalysts, we thought that C–H insertion/aromatic cyclo-addition of N -benzyl-enoldiazoacetamides could be a good indicator for the involvement of metal carbene intermediates. However, the use of highly electrophilic mercury(II) compounds with N -benzyl-enoldiazoacetamides has surprised us with its complexity and has led us to a novel Hg(OTf) 2 catalyzed intramolecular 1,4-addition reaction across the benzyl aromatic ring to form bicyclononatriene derivatives in high yield (Scheme 1).…”

Asymmetric Cyclopropanation Reactions

“…Zhou has reported a highly enantioselective mercury(II)catalyzed cyclopropanation of diazooxindoles and alkenes (Scheme 41). 124 The reaction worked well with both mono-and disubstituted alkenes, but stereoselectivity for highly substituted cyclopropanes was not given. The obtained spiroxindoles were diastereomeric with respect to those obtained with rhodium catalysis (see Scheme 23).…”