|Budget Amount *help
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥2,100,000 (Direct Cost: ¥2,100,000)
In the light promoted reaction of gamma -substituted allyltin reagents with carbonyl compounds, the allylic groups could be introduced predominantly at their a-position into carbonyl carbon via single electron-transfer from allylic tin reagent to the photoexcited triplet carbonyl compounds. The photoinduced alpha-allylation proceeds stereospecifically, for example, (E)- and (Z)-gamma-alkoxyallylic tin reagents give (R)- and (Z)-a-homoallylic alcohols. The photoinduced allylic 1,3-rearrangement has been also investigated in detail by direct excitation of y -substituted allyltin compounds.
In the reaction between a-alkoxyaldehydes and pentadienyltin, each of the possible four regio- and stereolsomers, syn-gamma-, anti-gamma-, syn-epsilon-, and syn-e-adducts, was selectively synthesized by the use of an appropriated combination of alkoxy groups. Lewis acids, and solvents. When MgBr2 was used as Lewis acid, the protecting a-oxygenated aldehyde such as benzyl (Bn) or methoxymethyl (MOM) affoided gamma-syn-adduct, but the combination of BF3OEt2 with a-protected aldehyde by tert-butyldimethylsilyl (TBS) gave a-anti-adduct, On the other hand, SnCI4 was found to give syn-gamma-adduct in the reaction with the benzyl protected aldehyde, When the reaction of the aldehyde protected by TBS was performed in the presence of InCl3 in ethanol media, gamma-anti-adduct was produced. Thus, the regio- and stereocontrolled allylation and pentadienylation of carbonyl group could be achieved by a appropriate combination of the reaction promoter and the protecting group of aldehyde.