Use of some aryl and heteroaryl nitrilimines and nitrones in the synthesis of spiroheterocycles

1,3‐Dipolar cycloadditions of C‐(5‐nitro‐2‐furyl)‐ N ‐methyl nitrilimine (2a) , C ‐(5‐nitro‐2‐furyl)‐ N ‐phenyl nitrilimine (2b) , C ‐4‐nitrophenyl‐ N ‐methyl nitrilimine (2c) and C,N ‐diphenyl nitrilimine (2d) with 1‐R‐substituted 3,3‐methylene‐5,5‐dimethylpyrrolidin‐2‐ones (1a‐d) where R is H, acetyl, 1,1‐dimethylethoxycarbonyl and 1‐methylethenyl proceed with complete regioselectivity in good yields to afford 1,3,7‐trisubstituted‐6‐oxo‐8,8‐dimethyl‐1,2,7‐triazaspiro[4,4]non‐2‐enes (5a‐g) exclusively. Cycloaddition of C ‐(5‐nitro‐2‐furyl)‐ N ‐phenylnitrone (3b) to the exocyclic double bond of the dipolarophile 1a proceeds to 2‐phenyl‐3‐(5‐nitro‐2‐furyl)‐6‐oxo‐8,8‐dimethyl‐1‐oxa‐2,7‐diazaspiro[4,4]nonane (7) with complete regio‐ and stereoselectivity.