A Novel Controlling Method for Regio- and Stereoselectivity in the Carbonyl-Allylation using Allylic Tin Reagents

在γ -取代烯丙基锡试剂与羰基化合物的光促反应中，烯丙基基团主要通过单电子转移从烯丙基锡试剂到光激发的三重态羰基化合物，在羰基碳的a位上被引入。光诱导α -烯丙基化进行立体特异性，例如，(E)-和(Z)- - -烷氧基锡试剂生成(R)-和(Z)- - -均烯丙基醇。通过直接激发y取代烯丙基锡化合物，对烯丙基1,3重排进行了详细的研究。在a-烷氧基醛与戊二乙烯基锡的反应中，通过使用适当的烷氧基组合选择性地合成了四种可能的区域和体合体，即正- γ -、反- γ -、正- ε -和正-e加合物。路易斯酸和溶剂。当使用MgBr2作为Lewis酸时，苯（Bn）或甲氧基甲基（MOM）等保护型氧合醛提供了γ -合合物，而用叔丁基二甲基硅基（TBS）将BF3OEt2与a-保护醛结合时，则产生了反-合合物，另一方面，在与苯保护醛的反应中发现SnCI4产生了-合-合物。产生了抗加合物。因此，通过反应促进剂与醛保护基团的适当结合，可以实现羰基的区域控制和立体控制的烯丙基化和戊二烯基化。

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.