In the presence of gallium chloride, dithioacetals reacted with allylstannanes to give the corresponding homoallyl sulfides in high yields. The present method could be applied to the chemoselective allylation of bis(dithioacetal) of keto aldehyde, and the dithioacetal arising from keto function reacted with allylstannane exclusively.
TaCl5-silicagel and TaCl5 as new Lewis acid systems for selective tetrahydropyranylation of alcohols and thioacetalisation, trimerisation and aldolisation of aldehydes.
TaCl5 adsorbed on silicagel has been utilized for the first time as Lewis acid catalyst for protection of aldehydes and alcohols as thiocetals and THP ethers respectively. Similarly TaCl5 has been exploited as an useful Lewis acid for chemoselective trimerisation and/or aldolisation of aldehydes. (C) 1997 Elsevier Science Ltd.
SAIGO, KAZUHIKO;HASHIMOTO, YUKIHIKO;KIHARA, NOBUHIRO;HARA, KEN-ICHI;HASEG+, CHEM. LETT.,(1990) N, C. 1097-1100