Padwa A, Hasegawa T, Liu B, Zhang Z
Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
J Org Chem. 2000 Oct 20;65(21):7124-33. doi: 10.1021/jo0009144.
A series of acyclic diazo ketoamides were prepared from N-benzoyl-N-alkylaminopropanoic acids and were treated with a catalytic amount of rhodium(II) acetate. The resultant carbenoids underwent facile cyclization onto the neighboring amide carbonyl oxygen atom to generate seven-membered carbonyl ylide dipoles. Subsequent collapse of the dipoles with charge dissipation produce bicyclic epoxides which undergo further reorganization to give substituted 5-hydroxydihydropyridones in good yield. Depending on the nature of the substituent groups, it was possible to trap some of the initially formed carbonyl ylide dipoles with a reactive dipolarophile such as DMAD. In other cases, cyclization of the dipole to the epoxide is much faster than bimolecular trapping. A related cyclization/rearrangement sequence occurred when diazo ketoamides derived from the cyclic pyrrolidone and piperidone ring systems were subjected to catalytic quantities of Rh(II) acetate. With these systems, exclusive O-cyclization of the amido group onto the carbenoid center occurs to generate a seven-ring carbonyl ylide dipole. Starting materials are easily prepared, and the cascade sequence proceeds in good yield and does not require special precautions. The overall procedure represents an efficient one-pot approach toward the synthesis of various indolizidine and quinolizidine ring systems.
由N-苯甲酰基-N-烷基氨基丙酸制备了一系列无环重氮酮酰胺，并将其用催化量的乙酸铑处理。生成的类卡宾容易环化到相邻的酰胺羰基氧原子上，生成七元羰基叶立德偶极子。随后偶极子随着电荷消散而塌缩，产生双环环氧化物，该双环环氧化物进一步重排，以良好的产率得到取代的5-羟基二氢吡啶酮。根据取代基的性质，有可能用诸如DMAD的活性亲偶极体捕获一些最初形成的羰基叶立德偶极子。在其他情况下，偶极子环化为环氧化物的速度比双分子捕获快得多。当衍生自环状吡咯烷酮和哌啶酮环系统的重氮酮酰胺用催化量的乙酸铑处理时，发生了相关的环化/重排序列。对于这些体系，酰胺基专一性地O-环化到类卡宾中心上，生成一个七元环羰基叶立德偶极子。起始原料易于制备，级联反应以良好的产率进行，并且不需要特殊的预防措施。整个过程代表了一种高效的一锅法合成各种吲哚里西啶和喹诺里西啶环系统的方法。
