RESUMO

The syntheses of the optically pure asymmetric hydroborating agents 1 (a, R = Ph; b, R = TMS) in both enantiomeric forms are reported. These reagents are effective for the hydroboration of cis-, trans- and trisubstituted alkenes. More significantly, they exhibit unprecedented levels of selectivity in the asymmetric hydroboration of 1,1-disubstituted alkenes (28-92% ee), a previously unanswered challenge in the nearly 50 year history of this reagent-controlled process. For example, the hydroboration of alpha-methylstyrene with 1a produces the corresponding alcohol 6f in 78% ee (cf., Ipc2BH, 5% ee). Suzuki coupling of the intermediate adducts 5 produces the nonracemic products 7 very effectively (50-84%) without loss of optical purity.

Assuntos

Álcoois/síntese química , Alcanos/síntese química , Alcenos/química , Boranos/síntese química , Alcanos/química , Boranos/química , Boroidretos/química , Modelos Moleculares , Conformação Molecular , Pseudoefedrina/análogos & derivados , Pseudoefedrina/química , Estereoisomerismo