Chemical and X‐Ray crystallographic characterization of the reaction products in the 1,3‐dipolar cycloaddition of diazomethane to p ‐toluquinone

The product 2 in the 1,3‐dipolar cycloaddition of one equivalent of diazomethane to p ‐toluquinone (1) was determined by 250 MHz nmr spectra to be approximately 85% 6‐methyl‐1‐ H ‐indazole‐4,7‐dione (2b). X‐ray crystallographic analysis was employed in the characterization of 1,6‐dimethyl‐1‐ H ‐indazole‐4,7‐dione (4a), which was the major 1‐ N ‐methyl regioisomer in the methylation of the cycloaddition mixture 2 with diazomethane. Methylation of the cycloaddition product 2 with diazomethane also provided a regioisomeric mixture of the 2‐ N ‐methyl derivatives 5. This mixture was synthesized for characterization by an independent method which utilized the cycloaddition of 3‐methylsydnone (10) to toluquinone (1). 1,5,6‐Trimethyl‐1‐ H ‐ind‐azole‐4,7‐dione (9) was found to be a minor product in the reaction of diazomethane with the cycloaddition product 2.