Cyclopropyl building blocks for organic synthesis, Part 106. Synthesis of spirocyclopropanated analogues of imidacloprid and thiacloprid

Abstract

tert-Butyl N-[1-(hydroxymethyl)cyclopropyl]carbamate (8) was converted into spirocyclopropanated analogues 14-CP and 14-CT of the insecticide Thiacloprid (2) in six simple steps with overall yields of 24% each, along with their regioisomers 13-CP and 13-CT in overall yields of 17 and 15%, respectively. The spirocyclopropanated analogues 27-CP and 27-CT of the insecticide Imidacloprid (1) were prepared from 8 in five steps in an overall yield of 10% each, along with their regioisomers 20-CP and 20-CT in an overall yield of 8 and 7%, respectively. The key step in all preparations was a cocyclization of an appropiately protected (1-aminocyclopropyl)methyl derivative with S,S-dimethyl cyanodithioirninocarbonate (11) or nitroguanidine (22). The structures of several final products and by-products were verified by X-ray crystal structure analyses.