9-Borabicyclo[3.3.2]decanes and the asymmetric hydroboration of 1,1-disubstituted alkenes.
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.
Gonzalez
Ana Z
AZ
University of Puerto Rico, Department of Chemistry, Rio Piedras, Puerto Rico.
Román
José G
JG
Gonzalez
Eduvigis
E
Martinez
Judith
J
Medina
Jesus R
JR
Matos
Karl
K
Soderquist
John A
JA
D000438:Alcohols / Q000138:chemical synthesis*; D000473:Alkanes / Q000138:chemical synthesis* / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry*; D001880:Boranes / Q000138:chemical synthesis* / Q000737:chemistry; D001894:Borohydrides / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D054199:Pseudoephedrine / Q000031:analogs & derivatives / Q000737:chemistry; D013237:Stereoisomerism
D000438:Alcohols; D000473:Alkanes; D000475:Alkenes; D001880:Boranes; D001894:Borohydrides; D054199:Pseudoephedrine; C012867:decane