Alkynyl sulfonamides undergo sequential 1,4- then 1,2-addition/rearrangement with lithium acetylides to yield enediynes in the absence of any promoters or catalysts. Mechanistic investigations suggest that the reaction proceeds via 1,4-conjugate addition of the nucleophile to the unsaturated system to give a key alkenyl lithium species which is stabilised by an intramolecular coordination effect by a sulfonamide oxygen atom. This species can be considered a vinylidene carbenoid given the carbon atom bears both an anion (as a vinyllithium) and a leaving group (the sulfonamide). The intramolecular coordination effect serves to stabilise the vinyllithium but activates the sulfonamide motif towards nucleophilic attack by a second mole of acetylide. The resulting species can then undergo rearrangement to yield the enediyne framework in a single operation with concomitant loss of aminosulfinate.

中文翻译：

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新型磺酰胺类非经典类胡萝卜素：烯二炔合成的机理研究†

在没有任何促进剂或催化剂的情况下，炔基磺酰胺与乙炔锂依次进行1,4-然后1,2-加成/重排，生成烯二炔。机理研究表明，反应通过亲核试剂的1，4-共轭加成到不饱和系统上，从而得到关键的烯基锂物质，该物质通过磺酰胺氧原子的分子内配位作用得以稳定。考虑到碳原子既带有阴离子（作为乙烯基锂）又带有离去基团（磺酰胺），该物种可以被视为亚乙烯基类化合物。分子内配位作用起到稳定乙烯基锂的作用，但激活磺酰胺基序，使其受到第二摩尔乙炔化物的亲核攻击。然后，所产生的物质可以在单个操作中进行重排以产生烯二炔构架，同时伴随着氨基亚磺酸盐的损失。