Tandem O–H Insertion/[1,3]-Alkyl Shift of Rhodium Azavinyl Carbenoids with Benzylic Alcohols: A Route To Convert C–OH Bonds into C–C Bonds

Abstract

Alcohols are among the most abundant and commonly used organic feedstock in industrial processes and academic research. The first tandem O-H insertion/[1,3]-alkyl shift reaction reported is between benzylic alcohols and rhodium azavinyl carbenoids derived from N-sulfonyl-1,2,3-triazoles, which provides a strategically novel way of cleaving C-OH bonds and forming C-C bonds. The substrate scope is broad, capable of covering 1°-, 2°-, and 3°-benzylic alcohols. Moreover, it constitutes a new and powerful synthetic method for constructing α-aminoketones. Mechanistic studies suggest that a [1,3]-alkyl shift of oxonium ylides is responsible for cleavage of the C-OH bonds.

Tandem Insertion–[1,3]‐Rearrangement: Highly Enantioselective Construction of α‐Aminoketones

“…Nevertheless, it remains attractive to search for straightforward and facile routes to gain optically pure α‐amino ketones from readily available starting materials. In this regard, tandem O−H insertion–sigmatropic rearrangement of Rh(II)‐carbene from N ‐sulfonyl‐1,2,3‐triazoles with alcohols has been employed for rapid construction of important compounds, including amino ketones using benzylic alcohols . However, the catalytic asymmetric version of this useful transformation remains elusive.…”

Rhodium(II)‐Catalyzed Reaction of 1‐Tosyl‐1,2,3‐triazoles with Morita–Baylis–Hillman Adducts: Synthesis of 3,4‐Fused Pyrroles

“…Soon afterwards, a novel protocol for the synthesis of unsymmetrical indigo‐like ( E )‐α‐amino enaminones by rhodium catalyzed O−H insertion and subsequent rearrangement of isatins with 1‐tosyl‐1,2,3‐triazoles has also been reported by us . Up to now, the direct O‐H insertions of α‐imino rhodium carbenoids with proper substrates, taking benzylic alcohol for example, have been well studied. Moreover, some methods have been developed for the construction of nitrogen‐containing heterocycles (such as pyrrole skeleton) based on O−H insertion and subsequent rearrangement .…”

The Expanding Utility of Rhodium‐Iminocarbenes: Recent Advances in the Synthesis of Natural Products and Related Scaffolds

“…This process greatly simplified the experimental procedure compared with utilizing diazo precursor because triazoles are relatively more stable and safer for routine handling in laboratory. This milder and slower liberated carbene (commonly as acceptor or donor/acceptor carbene) are more chemoselective and have been known to undergo a variety of useful transformations, such as cyclopropanation, C−H bond and X−H (X=heteroatoms) bond insertion, 1,2‐alkyl migration, [2,3] sigmatropic rearrangement [17] and other novel reactions based on the inherent properties of metal carbenes . Additionally, due to the presence of the nucleophilic imine nitrogen atom in the unique iminocarbene 3 , it usually exhibit more diverse reactivities due to the potential participation of imino group in the reactions.…”

“…However,n ew nondiazo approaches to metal carbenes have recently attracted considerable attention due to the hazardous and dangerousn ature of diazo compounds. [8] In recent years, as pioneered by Fokin, [9] Gevorgyan, [10] andM urakami groups, [11] N-Sulfonyl-1,2,3-triazoles,w hich can be readily prepared from terminala lkynes by copper-catalyzed 1,3-dipolar cycloaddition with N-sulfonyl azides, [12] have emerged as stable and convenient metal iminocarbene precursors and openedu panew avenue in carbenoid chemistry.T his interesting chemistry started from aD imorthtype equilibrium of triazole (1)t oa na-diazo imine 2,i nt he presenceo farhodiumo rn ickel catalyst (Scheme 1) and provided the highly reactive a-imino metal-carbene 3.T his process greatlys implified the experimental procedure compared with utilizingd iazo precursor because triazoles are relatively more stable and safer for routine handling in laboratory.T his milder and slower liberated carbene (commonlya sa cceptor or donor/acceptor carbene) are more chemoselective and have been known to undergo av ariety of useful transformations, such as cyclopropanation, [13] CÀHb ond [14] and XÀH( X = heteroatoms) bond insertion, [15] 1,2-alkyl migration, [16] [2,3] sigmatropic rearrangement [17] and other novel reactions based on the inherent properties of metal carbenes. [18] Additionally,d ue to the presence of the nucleophilic imine nitrogen atom in the unique iminocarbene 3,i tu sually exhibit more diverse reactivities due to the potentialp articipation of imino group in the reactions.T hus it offersa ne fficient shortcut for the synthesis of nitrogen-containing heterocycles.…”