Hydrosilylation of Aldehydes and Ketones Catalyzed by Half‐Sandwich Manganese(I) N‐Heterocyclic Carbene Complexes

Abstract

International audienc

Manganese N‐Heterocyclic Carbene Complexes for Catalytic Reduction of Ketones with Silanes

“…All ketone substrates were converted within 1–5 h when using 5 , whereas 1 needed slightly longer reaction times (2–8 h), depending on the substrates. Both catalysts 1 and 5 tolerated fluoro, chloro, and bromo functionalities (entries 3–10, Table ), in contrast with other Mn‐based catalysts, reported to be inactive in the presence of chloro‐ and bromo‐substituents . For the p ‐iodo‐benzaldehyde, reductive dehalogenation occurred and formation of 1‐phenyethanol was detected by NMR spectroscopy.…”

“…Trovitch and colleagues elegantly proved that the concurrent modified Ojima and Mn–H insertion mechanisms were responsible for catalysis with a Mn 0 catalyst . Identification of Mn–H species was also achieved by Lugan, Sortais, and co‐workers with CpMn(NHC)(CO) 2 systems . In contrast, a radical transfer mechanism has been proposed by Trovitch and co‐workers with a Mn complex bearing a redox‐active ligand …”

“…However, until now, catalysis with Mn‐NHC has been poorly explored . In particular, in hydrosilylation reactions, the only examples of well‐defined Mn‐NHC complexes were recently reported by Lugan, Sortais, and co‐workers …”

Recent Advances of Manganese Catalysis for Organic Synthesis

“…Lavigne et al reported that the manganese N-heterocyclic carbene (NHC) complex 146 would catalyse the reduction of a variety of aryl and aliphatic aldehydes and ketones under UV irradiation (Table 1). [45] The electronics and sterics of the substituents on the carbene ligand were altered with mesityl substituents giving the best yields.…”

A Manganese N‐Heterocyclic Carbene Catalyst for Reduction of Sulfoxides with Silanes

“…Motivated by these findings, we became interested in further exploring the potential of [Mn(bis‐NHC)(CO) 3 Br] complexes in reductions with silanes. Surprisingly, despite the enormous success of metal NHC complexes in catalysis, very few catalytic applications of Mn‐NHC complexes can be found in the literature . We report in this work the deoxygenation of sulfoxides to sulfides with silanes mediated by the manganese complex [Mn(bis‐NHC)(CO) 3 Br] bearing a bis‐N‐heterocyclic carbene ligand.…”