Transannular cyclization reactions of cyclooctane-1,5-dione and 5-ethoxycarbonylmethylenecyclooctanone upon treatment with diamines. An efficient one-pot synthesis of substituted 2,6-diazatricyclo[5.3.3.01,6]- and 2,5-diazatricyclo[4.3.3.01,5]-alkanes and a study of their acetylation products

Abstract

Cyclooctane-1,5-dione 1 undergoes transannular cyclization upon treatment with 1,2-diaminoarenes 2a–d or 1,3-diaminopropane 5a to afford the 2,5-diazatricyclo[4.3.3.0^1,5]dodecan-6-ols 3a–d or 2,6-diazatricyclo[5.3.3.0^1,6]tridecan-7-ol 6 respectively, in moderate to good yields. The ethoxycarbonylmethyldiazatricyclo analogues 22a,b result from a similar reaction of 5-ethoxycarbonylmethylenecyclooctanone 19 with diaminoalkanes 5a,b. Acetylation of tricyclo compound 3d leads, among others, to the unexpected product 2-diacetylmethylidene-1-(5-oxocyclooct-1-en-1-yl)-3-methyl-2,3-dihydrobenzimidazole 12.