Synthesis and Reactions of Cyclic Carbodiimides

Article abstract of DOI:10.1021/jo00158a022

Modified Tiemann rearrangement on cyclic amidoxime O-methanesulfonates 4 has been used to synthesize cycloalkylene carbodiimides 1 and 4,5,6,7-tetrahydrobenzo-1,3-diazonine (1g). 1,3-Diazacycloocta-1,2-diene (1b), 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 1d (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-1,2-diene (1a, 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=NC6H5).