Li Xianfeng, Chen Jian J., Tanner Dennis D.
Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2.
J Org Chem. 1996 Jun 26;61(13):4314-4318. doi: 10.1021/jo960043r.
The mechanisms for the reaction of allyltributylstannane with a number of fragmentation probes, alpha-substituted acetophenones, were studied. All reactions were shown to proceed through free radical chain sequences since they could be initiated by AIBN and inhibited by m-dinitrobenzene (DNB). alpha-Halo- and alpha-(benzoyloxy)acetophenones (I and II, PhCOCR(1)R(2)X; X = F, Cl, Br, OCOPh; R(1), R(2) = H, Me) yielded the allylation products, PhCOCR(1)R(2)CH(2)CH=CH(2)), through a chain sequence involving as the propagation step: an electron transfer from Bu(3)Sn() to I and II, fragmentation of the ketyl anion PhCOCR(1)R(2)X()(-), and addition of PhCOCR(1)R(2)(*) to allyltributylstannane. The reactions of alpha-(arylsulfonyl)acetophenones (IIIa-c, PhCOCR(1)R(2)Y, Y = SO(2)Tol-p), however, gave a nearly 1:1 mixture of allyl tosyl sulfone and the corresponding ketone, PhCOCHR(1)R(2). The (1)H and (13)C NMR of the reaction mixture between allyltributylstannane and alpha-(p-methylbenzenesulfonyl)isobutyrophenone substantiated the intermediacy of the tin enolate PhC(OSnBu(3))=CMe(2). These results suggested that a radical addition elimination mechanism was involved in the reactions of IIIa-c with allylstannane. The reaction of alpha-phenylthioacetophenone (IV, PhCOCH(2)SPh) gave both the electron transfer and the addition elimination products (PhCOCH(2)CH(2)CH=CH(2), PhCOCH(3)), indicating that both pathways were involved in the formation of the products.
研究了烯丙基三丁基锡与多种裂解探针（α-取代苯乙酮）的反应机制。所有反应均显示通过自由基链反应序列进行，因为它们可由偶氮二异丁腈引发并被间二硝基苯（DNB）抑制。α-卤代苯乙酮和α-（苯甲酰氧基）苯乙酮（I和II，PhCOCR(1)R(2)X；X = F、Cl、Br、OCOPh；R(1)，R(2) = H、Me）通过一个链反应序列生成烯丙基化产物PhCOCR(1)R(2)CH(2)CH=CH(2)，该序列的传播步骤包括：从Bu(3)Sn()到I和II的电子转移、酮基阴离子PhCOCR(1)R(2)X()(-)的裂解以及PhCOCR(1)R(2)(*)与烯丙基三丁基锡的加成。然而，α-（芳基磺酰基）苯乙酮（IIIa - c，PhCOCR(1)R(2)Y，Y = SO(2)Tol - p）的反应生成了烯丙基甲苯磺酰砜和相应酮（PhCOCHR(1)R(2)）的近1:1混合物。烯丙基三丁基锡与α-（对甲基苯磺酰基）异丁酰苯反应混合物的(1)H和(13)C NMR证实了烯醇锡盐PhC(OSnBu(3))=CMe(2)的中间体性质。这些结果表明，IIIa - c与烯丙基锡的反应涉及自由基加成消除机制。α-苯硫基苯乙酮（IV，PhCOCH(2)SPh）的反应生成了电子转移产物和加成消除产物（PhCOCH(2)CH(2)CH=CH(2)，PhCOCH(3)），表明两种途径都参与了产物的形成。
