Highly Stereoselective Cationic Cyclization Assisted by a Sulfenyl Group. Scope, Limitation, and Mechanism
作者:Changqing Liu、Kazuaki Kudo、Yukihiko Hashimoto、Kazuhiko Saigo
DOI:10.1021/jo951128f
日期:1996.1.1
When 8-acetoxy-2-methyl-9-(phenylthio)-2-nonene (1a) was treated with an acid, followed by a base, alkylative cyclization proceeded to give a mixture of 1,2-disubstituted cyclohexanes: 2a, 3a, and 4a. The stereochemistry of the reaction was only slightly affected by the leaving group and the reaction conditions, such as the temperature, solvent, and acid. However, the bulkiness of the sulfenyl group
用酸处理8-乙酰氧基-2-甲基-9-(苯硫基)-2-壬烯(1a),然后进行碱处理时,进行烷基化环化反应,得到1,2-二取代的环己烷的混合物:2a,3a和4a。反应的立体化学仅受离去基团和反应条件如温度,溶剂和酸的影响很小。但是,亚磺酰基的庞大度对反应的立体化学过程有很大的影响。当将1c(1a的亚砜基更大的衍生物)用作底物时,可实现高反式选择性。另一方面,底物的碳链的长度和刚性也对反应的立体化学有重要影响。当使用10a(一种碳原子较少的1a类似物)或15a(碳链中双键比1a多的衍生物)作为底物时,观察到了很高的顺式选择性。反应通过6,5-或5,5-稠环中间体进行。亚磺酰基基团辅助反应对于α-亚磺酰基化仲醇的乙酸酯的立体选择性环化可能是有用的方法。