Synthesis and Reactions of Cyclic Carbodiimides

Abstract

Modified Tiemann rearrangement on cyclic amidoxime O-methanesulfonates 4 has been used to synthesize cycloalkylene carbodiimides 1 and 4,5,6,7-tetrahydrobenzo-l,3-diazonine (1g). 1,3-Diazacycloocta-1,2-diene (lb, n = 5) was also prepared by dehydrosulfuration of pentamethylenethiourea. [2 + 2] cycloadducts of the type 20 and 21 are readily formed from 1 as well as 1g with aryl isocyanates and N,N′-diphenylcarbodiimide. Hexafluoroacetone and Id (n = 7) give a dioxazane, 24b (n = 7), while 1c (n = 6) produces inseparable mixtures of 24a (n = 6) and oxazetidine 23. 1,3-Diazacyclohepta-l,2-diene (la, n = 4) oligomerizes on preparation from tetramethylenethiourea, giving predominantly cyclodimer 7 and trimer 8 (not isolated); it can also be trapped with N,N′-diphenylcarbodiimide to give 20a (n = 4, X = NC6H6). © 1983, American Chemical Society. All rights reserved.