Synthesis of 2-Substituted Benzofurans and Indoles Using Functionalized Titanium Benzylidene Reagents on Solid Phase
作者:Calum Macleod、Gordon J. McKiernan、Emma J. Guthrie、Louis J. Farrugia、Dieter W. Hamprecht、Jackie Macritchie、Richard C. Hartley
DOI:10.1021/jo026384o
日期:2003.1.1
nitrogen nucleophile in the ortho position were generated from thioacetals, using low-valent titanocene complex, Cp2Ti[P(OEt)3]2. Methylene acetal, alkyl ether, silyl ether, fluoro, tertiary amino, and N-alkyl, N-benzyl, N-prenyl, and N-silyl tert-butyl carbamate groups were tolerated in the titanium alkylidene reagents (Schrock carbenes). Aryl-chlorine bonds were stable to the titanium benzylidene functionality
使用低价的钛茂配合物Cp2Ti [P(OEt)3] 2,由硫缩醛生成在邻位带有掩蔽的氧或氮亲核试剂的钛(IV)亚苄基。亚甲基缩醛,烷基醚,甲硅烷基醚,氟,叔氨基和N-烷基,N-苄基,N-异戊烯基和N-甲硅烷基叔丁基氨基甲酸酯在钛亚烷基试剂(Schrock carbenes)中是可容忍的。芳基-氯键对钛亚苄基官能团稳定,但是在芳基氯存在下,对于硫代缩醛的还原,其化学选择性差。钛亚苄基钛将Merrifield和Wang树脂结合的酯转化为烯醇醚。氧亲核试剂被掩盖为TMS醚,并且当将带有该邻位取代基的树脂结合的烯醇醚用1%TFA的二氯甲烷溶液处理时,苯并呋喃以高收率从树脂中释放出来。变色龙捕获策略确保了出色的纯度。以类似的方式,将N-烷基化和N-甲硅烷基化的氨基甲酸叔丁酯分别用于合成N-烷基和N-Boc吲哚。这些杂环的无痕固相合成被认为涉及切割后修饰而不是环化终止。