Asymmetric Desymmetrization via Metal‐Free C−F Bond Activation: Synthesis of 3,5‐Diaryl‐5‐fluoromethyloxazolidin‐2‐ones with Quaternary Carbon Centers

Abstract

We disclose the first asymmetric activation of a non‐activated aliphatic C−F bond in which a conceptually new desymmetrization of 1,3‐difluorides by silicon‐induced selective C−F bond scission is a key step. The combination of a cinchona alkaloid based chiral ammonium bifluoride catalyst and N,O‐bis(trimethylsilyl)acetoamide (BSA) as the silicon reagent enabled the efficient catalytic cycle of asymmetric Csp3−F bond cleavage under mild conditions with high enantioselectivities. The ortho effect of the aryl group at the prostereogenic center is remarkable. This concept was applied for the asymmetric synthesis of promising agrochemical compounds, 3,5‐diaryl‐5‐fluoromethyloxazolidin‐2‐ones bearing a quaternary carbon center.

Catalyst-free carbosilylation of alkenes using silyl boronates and organic fluorides via selective C-F bond activation

“…Besides, the aryl and alkyl fluorides have never been used for the three-component carbosilylation of alkenes. Our group has been engaged in the development of efficient methods for the selective functionalization of C( sp 2 )-F and C( sp 3 )-F bonds under mild conditions both with 58 or without 58 – 61 the use of transition metals. In this context, our recent report on the defluorosilylation of organic fluorides using silyl boronates and with or without a Ni catalyst 58 inspired us to undertake a much more challenging research topic: the difunctionalization of alkenes with aryl or alkyl fluorides in the presence of silyl boronates via C–F bond cleavage (Fig.…”

Defluorosilylation of fluoroarenes and fluoroalkanes

“…While a wide range of methods for the synthesis of organosilicon compounds have been developed, methods for the transformation of fluoroarenes into aryl silanes do not exist. Prompted by the versatility and pivotal role of organosilicon compounds 16 , as well as by our ongoing interest in the activation of inert C–F bonds 17 , we report herein an available example of the ipso -silylation of aryl and alkyl fluorides via cleavage of unactivated C–F bonds under catalytic conditions mediated by Ni or in the absence of metal catalyst (Fig. 1c ).…”

Controlled Synthesis of One-Handed Helical Polymers Carrying Achiral Organoiodine Pendants for Enantioselective Synthesis of Quaternary All-Carbon Stereogenic Centers

“…In this context, asymmetric dearomatization of phenols and the relevant electron-rich aromatic compounds has been regarded as an effective method for the synthesis of such cyclic molecules. − Chiral hypervalent iodine organocatalysts can effectively catalyze dearomatization of phenols, giving a variety of transformations that are hard to be achieved by others catalysts. ,− Thanks to the pathbreaking contributions by Kita et al, Ishihara et al, and so on, remarkable progress has been achieved using chiral organoiodine catalysts for enantioselective spirolactonization and hydroxylative phenol dearomatization. , However, developing chiral hypervalent iodine organocatalysts with high catalytic efficiency and satisfactory enantioselectivity still remains a challenging task. Moreover, asymmetric synthesis of a spiro-stereogenic quaternary all-carbon center is a daunting and long-standing challenge in organic synthesis. − Therefore, creating novel and green catalysts to realize this end is very interesting and of great value.…”