Cooperative organocatalysis of Mukaiyama-type aldol reactions by thioureas and nitro compounds

Abstract

A unique organocatalytic system for Mukaiyama-type aldol reactions based on the cooperative action of nitro compounds and thioureas has been identified. This system is compatible with a wide range of substrates and does not require low temperatures, inert atmospheres, or an aqueous workup. A catalytic mechanism based on nitro group-mediated silyl cation transfer has been proposed.

Triflimide: An Overlooked High‐Performance Catalyst of the Mukaiyama Aldol Reaction of Silyl Ketene Acetals with Ketones

“…Regarding non‐asymmetric Mukaiyama aldol reactions of SKAs with ketones, a metal‐catalyzed method (CuF⋅3 PPh 3 ⋅2 EtOH with (EtO) 3 SiF) and a Lewis base‐catalyzed method (sodium phenoxide‐phosphine oxide) have been reported (Scheme C). Alternatively, organocatalytic systems such as C−H acids,, a hydrogen‐bond‐assisted disulfonimide catalyst and Schreiner's thiourea catalyst in combination with nitro compounds have previously been investigated with some success. Despite these advances, however, a catalytic method that is convenient, broadly applicable, practical, and scalable remains desirable.…”

An efficient organopromotor L‐arginine facilitated synthesis of thiazolo[3,2‐a]pyrimidine derivatives in EtOH:H2O solvent

“…To encourage this concept, the last two decades have involved organocatalysis [1,5,6] as a powerful catalytic route, enhancing the chemical reactions without the necessity of metal atoms [7][8][9]. The quest for efficient and "greener" catalysts was not only aimed at substituting toxic and expensive metal catalysts, but it was also a pursuit for extremely sensitive and highly substratespecific biocatalysts [10][11][12]. Ideal organocatalysts have various advantages such as they are nontoxic, commercially available, easy to use, cheap, robust, and ecofriendly [8].…”

Cooperativity in the Aldol Condensation Using Bifunctional Mesoporous Silica–Poly(styrene) MCM-41 Organic/Inorganic Hybrid Catalysts

“…In recent years, researchers have drawn inspiration from highly efficient biological systems to develop engineered materials that promote a series of reactions using enzymatic catalysis. − In parallel, scientists have adapted these biological principles into the synthetic realm to engineer materials capable of enhanced activity toward cooperatively catalyzed reactions or cascade reaction networks. In some cases, catalysts require spatial sequestering with the use of a multitude of domains due to incompatibility of active catalyst sites in some cascade reactions. − In other instances, reactions targeting cooperative activation of substrates, cohabitation of catalyst sites in close proximity becomes a design feature. − In both cases, functionalized materials such as polymers, ,− , mesoporous silicas, ,,,,,− ,, zeolites, , and metal–organic frameworks have been used as platforms to host molecular active sites for these purposes. These supports offer significant advantages due to their high surface areas, ease of functionalization, stability, and sometimes inherent catalytic properties.…”