Cascade Radical Cyclizations of Benzannulated Enyne−Allenes. Unusual Cleavage of a Benzene Ring Leading to Twisted 1,1‘-Dialkyl-9,9‘-bifluorenylidenes and Spiro[1<i>H</i>-cyclobut[<i>a</i>]indene-1,9‘-[9<i>H</i>]fluorenes]
作者:Yonghong Yang、Jeffrey L. Petersen、Kung K. Wang
DOI:10.1021/jo030147j
日期:2003.7.1
9'-[9H]fluorene] 20 apparently was produced via two intramolecular [2 + 2] cycloaddition reactions of the benzannulated enyne-allene moieties, generated in situ from the benzannulated enediynyl propargylic alcohols. The twisted 1,1'-dimethyl-9,9'-bifluorenylidene 33 and the spiro[1H-cyclobut[a]indene-1,9'-[9H]fluorene] 39 (trans/cis = 3:1) were likewise produced from 32 and 38, respectively.
用亚硫酰氯处理苯并环化的二炔基炔丙醇16(异构体比例= 2:1),引发一系列反应,导致扭曲的1,1'-二丙基-9,9'-联芴基17,多环化合物18和19,和螺[1H-环丁[a]茚-1,9'-[9H]芴] 20(反式/顺式= 5:1)。从16到出乎意料的17的转变大概涉及苯甲环烯-烯丙烯21的初始形成,然后进行C(2)-C(6)环化反应和分子内自由基-自由基偶联反应,从而形成正式的Diels- Alder加合物23。重复该序列,然后提供24。连接具有丙基取代基的两个碳的键的断裂得到25。随后,连接两个中心五元环的碳-碳键的旋转随后得到反式异构体26 。26可能被氧气氧化,然后水解,然后生成17。有趣的是,导致17的途径涉及苯环的不寻常裂解。17的X射线晶体结构表明,其对于连接两个联芴基片段的碳-碳双键具有45.2度的扭转角。螺[1H-环丁[a]茚-1,9'-[9H]芴] 20显然是由苯并环烯炔-丙二烯部分的两个分子内[2