The reactions of diazo compounds with lactones. Part 1. Cyclopropanespiro-β-lactones from diketene: synthesis and reactions
作者:Paul V. Murphy、Timothy J. O’Sullivan、Niall W. A. Geraghty
DOI:10.1039/b001393p
日期:——
The cyclopropanespiro-β-lactones 3, 4 and 12 can be prepared by the metal catalysed, or photochemically promoted decomposition reactions of diazocompounds in the presence of diketene. The thermal reactions of these compounds give a variety of products depending on the nature of the spirolactone; these include a furan 9a, 1,4-dicarbonyl compounds 18aâc and 19b, a pyranone 20b, furanones 21a, 21f and 22a and the enol 16. The boron trifluoride promoted reaction of a mixture of 3b and 4b gives a β-ketoacid. Mechanisms are proposed for the formation of these products. The rearrangment of the cyclopropanespiro-β-lactones to furan-2(5H)-ones and furan-2-(3H)-ones 6â8, 21a, 21f, 22a and 24 is shown to be a general reaction that involves metal catalysis. A mechanism based on formation of a metallocycle by a novel insertion of the metal into the CâO bond of the β-lactone ring is proposed for this rearrangement. This accounts for the observed features of the reaction.
环丙烷螺-β-内酯3、4和12可以通过金属催化或光化学促进的双氮化合物在二酮存在下的分解反应制备。该类化合物的热反应根据螺内酯的性质会产生多种产品,包括呋喃9a、1,4-二酮化合物18a–c和19b、吡喃酮20b、呋喃酮21a、21f和22a以及烯醇16。三氟化硼促进的3b和4b混合物的反应产生β-酮酸。针对这些产物的形成提出了反应机理。环丙烷螺-β-内酯转变为呋喃-2(5H)-酮和呋喃-2-(3H)-酮6–8、21a、21f、22a和24的重排被证明是一个涉及金属催化的一般反应。对于这一重排,提出了一种基于金属通过新颖的插入方式进入β-内酯环的C–O键形成金属环的机理。这解释了反应中观察到的特征。