Synthesis of Olefins by Formal Carbene Coupling

Abstract

In this review, the coupling of two carbene precursors for the synthesis of alkenes is surveyed.The key to selective carbene coupling is the difference in the rate of carbene generation between the two carbene precursors. This strategy requires judicious selection between two carbene precursors as well as fine-tuning of reaction conditions to obtain the desired chemo-and stereoselectivity. These couplings were carried out in the presence and absence of a metal catalyst. The present review describes inter-and intramolecular coupling of diazo compounds and cross-coupling between diazo and non-diazo compounds. 1.Introduction 2.

Reactivity of Nickel Complexes Bearing P(C═X)P Ligands (X = O, N) Toward Diazoalkanes: Evidence for Phosphorus Ylide Intermediates

“…This reaction is known for a wide variety of metals (Ru, Rh, Fe, Co, Cu, Mo, Ir) with catalytic applications. 4,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]44 A similar reaction was reported in 1998 by Gong and co-workers performing a Wittig-type reaction on (PCy 3 ) 2 Ni(η 2 -CO 2 ) yielding a ketene. 45 In addition, the formation of unsymmetrical olefins from ketones and dihaloalkanes in the presence of stoichiometric amounts of (Et 3 P) 4 Ni has been ascribed to a carbene/ylide pathway.…”

Insights into the multifaceted applications of vinyl sulfoxonium ylides

“…Moreover, the feasible carbene dimerization, which is the most common reaction of metal carbene in the absence of an external trapping agent has not occurred. 32…”

“…Moreover, the feasible carbene dimerization, which is the most common reaction of metal carbene in the absence of an external trapping agent has not occurred. 32 Despite, it being a good approach for the synthesis of furans from vinyl sulfoxonium ylides, this pathway will be the most competitive reaction for the trapping of other nucleophiles in intermolecular addition to the in situ generated carbene. Thus, carbene transfer reactions of Z-selective vinyl sulfoxonium ylides require more nucleophilic heteroatoms such as amines or thiols.…”

Stereoselective gem-Difunctionalization of Diazo Compounds with Vinyl Sulfoxonium Ylides and Thiols via Metalloradical Catalysis

“…To achieve this challenging transformation, the following issues must be addressed: (i) In general, both carbenes can react with the X-H bond of the nucleophile to undergo X-H insertion as shown in Scheme b . (ii) Carbene-mediated homo- or cross-dimerization could lead to both possible geometrical isomers of alkenes . (iii) The dimerized product obtained from the electron-withdrawing group containing a carbene precursor can act as a Michael acceptor and is prone to undergo conjugate addition by the nucleophilic heteroatom of X-H .…”