A Facile Cascade Synthesis of 5,6-Diaryldibenzo[<i>a</i>,<i>e</i>]cyclooctenes from (<i>Z</i>,<i>Z</i>)-1-Aryl-3,5-octadiene-1,7-diynes
作者:Kung K. Wang、Chongsheng Shi、Jeffrey L. Petersen
DOI:10.1021/jo9802473
日期:1998.6.1
Sequential treatment of (Z)-3-methyI-2-penten-4-ynal (10) with the allenylborane 2 and 8-aminoethanol furnished II. The use of II for cross-coupling with aryl iodides followed by the KH-induced syn elimination of the coupled adducts 13 provided easy access to a variety of dienediynes 14 for subsequent conversions to dibenzo[a,e]cyclooctenes (sym-dibenzocyclooctatetraenes) 17. By cross-coupling with 1,2- and 1,4-diiodobenzene, it was possible to obtain 19 and 25 having two dienediynyl moieties. It was anticipated that the oligomers 21 and 26 containing multiple dibenzo[a,e]cyclooctenyl units could thus be synthesized. The H-1 NMR spectrum of 32 having three dibenzo[a,e]cyclooctenyl units indicates the presence of three diastereomers 32a-c in a random statistical distribution of 2:1:1. Similarly, the H-1 NMR spectrum of 33 having two dibenzo[a,e]cyclooctenyl units exhibits signals that support the presence of two diastereomers 33a and 33b ina 1:1 ratio.