Sakurai-Hosomi reaction complexes

It has also been shown that the Sakurai-Hosomi reaction of methallylsilanes with glyoxylates is catalyzed by the BINOL-Ti complex (1) to give the products, surprisingly, in an allylic silane (ene product) form with high enantioselecdvity (Scheme 8C.22) [53],... 

Asymmetric Hetero Diels-Alder Reaction. In contrast to the CAB catalyst (2 R = H) which is stable and both air and moisture sensitive, the B-alkylated CAB catalyst (3 R = Ph or alkyl) is stable and can be stored in a closed container at rt. A solution of the CAB (3 R = Ph) catalyzes Diels-Alder, aldol, and Sakurai-Hosomi reactions. Although the asymmetric inductions achieved by these complexes are slightly less efficient than that of the corresponding hydride-type catalyst, the CAB catalyst (3 R = Ph) is shown to be an excellent system for hetero Diels-Alder reactions. 

Inl989, Yamamoto introduced the chiral (acyloxy)borane (CAB) complex for catalytic asymmetric Diels-Alder reactions [18], which has been utilized as a magic hand catalysis for the aldol synthesis and for the Sakurai-Hosomi reaction so far [19,20]. In contrast to R=H of 17, which is both air and moisture sensitive, the B-alkylated catalyst, R=Ph or alkyl, is stable and can be stored in closed containers at room temperature. This catalyst is easily prepared from phenyl- or alkylboric acid and 16 simple mixing of a 1 1 molar ratio of the ester 16 and phe-... 

An enantio- and diastereoselective Sakurai-Hosomi reaction catalyzed by scan-dium-pybox complexes (10-15 mol%) has been developed [117]. Both alkyl-and aryl-substituted allylsilanes are effective coupling partners with N-phenyl-glyoxamide (64-89%, antilsyn = 9/1-99/1, 91-99% ee (anti)). Applications of this reaction to the asymmetric syntheses of N-Boc o-alloisoleucine and D-isoleucine have been described. 

Hosomi-Sakurai reaction, allylsilations, 9, 305 Host complexes calixarenes as, 12, 799 crown-ethers as, 12, 813... 

Substituted allylsilanes are subject to ene reaction with aldehydes and a,/3-unsaturated carbonyl compounds in the presence of a Lewis acid. The Et2AlCl-promoted reaction of /3-siloxymethyl-substituted allylsilane 27 with aldehydes gives more functionalized allylsilanes (Equation (37)).148 The use of TiCU instead of Et2AlCl leads to the Hosomi-Sakurai allylation. Catalytic enantioselective carbonyl-ene reactions of methallylsilanes have been achieved by using chiral Ti and A1 complexes.149,150... 

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