A very simple and convenient one-pot synthesis of spiro-3,4-dihydro-2H-pyrrole has been developed while synthesising the 2,2,5-trisubstituted pyrrolidines. Initially, the Meldrum’s acid has been treated with ,-unsaturated ketones in presence of anhydrous carbonate base and phase transfer catalyst benzyltriethylammonium chloride in acetonitrile to afford the Michael adduct which is readily converted to the corresponding oxime using standard conditions. The crude oxime is treated directly with p-toluenesulfonyl chloride and in presence of excess organic base results in tandem nucleophilic cyclisation product spirobicyclic as spiro-3,4-dihydro-2H-pyrrole directly, instead the tosyloxime as product.

中文翻译：

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通过串联亲核环化反应一锅合成螺-3,4-二氢-2H-吡咯

在合成 2,2,5-三取代吡咯烷的同时，开发了一种非常简单方便的螺-3,4-二氢-2H-吡咯的一锅合成方法。最初，在无水碳酸盐碱和相转移催化剂苄基三乙基氯化铵的乙腈存在下，用 α,-不饱和酮处理 Meldrum 酸，得到迈克尔加合物，使用标准条件很容易将其转化为相应的肟。粗肟直接用对甲苯磺酰氯处理，并在过量有机碱的存在下产生串联亲核环化产物螺双环，直接作为螺-3,4-二氢-2H-吡咯，而不是作为产物的甲苯磺酰肟。