Cyclohexylideneacetyl Isothiocyanate. Precursor for the Synthesis of 1,3-Thiazaspirocycloalkanes and 1,3-Diazaspirocycloalkanes

The N -(4-substituted phenyl)- N' -cyclohexylideneacetylthioureas IIa - IIf were readily prepared by the reaction of cyclohexylideneacetyl isothiocyanate I with 4-substituted anilines. They were cyclized to the 2-(4-substituted phenylimino)-4-oxo-1,3-thiazaspiro[5.5]undecanes IIIa - IIIe in the presence of boron trifluoride etherate and to the 1-(4-substituted phenyl)-4-oxo-2-thioxo-1,3-diazaspiro[5.5]undecanes IVa , IVc - IVf in alkaline medium.