182805-86-3Relevant articles and documents
TiIV-BINOLate-Catalyzed Highly Enantioselective Additions of β-Substituted Allylstannanes to Aldehydes
Weigand, Stefan,Brueckner, Reinhard
, p. 1077 - 1084 (2007/10/03)
Enantiomerically pure homoallyl alcohols were prepared from aldehydes R1-CH=O (R1 = Ph, pentyl, Ph-CH=CH-, iPr) and β-substituted allylstannanes H2C=CR2-CH2-SnBu3 (R2 = pentyl, tBuPh2SiO-CH2-, tBuPh2SiO-CH2-CH2-, PhS-CH2-CH2).These reactions were catalyzed by the same additives-Ti(OR)4 (10 molpercent) and (R)-BINOL (20 molpercent)- that Keck et al. used in analogous reactions with methallyl- and allyltributylstannane.To attain optimum ee values (96.4-99.2percent in the reaction with hexanal) these additives had to be premixed for 2 h at room temperature.Ti(OEt)4 and Ti(OiPr)4 gave equally good results, while Ti(OMe)4, Ti(OCHEt2)4 and Ti(OtBu)4 were inferior.Our procedure works in the absence of molecular sieves and can be extended to enantioselective addition reactions with allyl- and methallyltributylstannane, too (+ hexanal: 97.4 and 97.0percent ee, respectively). -Keywords: allylstannanes; asymmetric allylations; catalysis; C-C bond formation; homoallylic alcohols