“Dry” and “Wet” Green Synthesis of 2,2′‐Disubstituted Quinazolinones

An extremely convenient, environmentally benign spirocyclization under either aqueous or solventless conditions, developed for the preparation of spiro[cyclohexane‐1,2′‐(1′ H )‐quinazolin]‐4′(3′ H )‐one ( 3 ), has been utilized to convert α‐ and β‐aminocarboxamides 5a , 5b , 6a – c and 9 and cycloalkanones 2 – 2b and alkanones 2c – e into 1,4‐diazaspiro[4.5]decan‐2‐one ( 10 ) and cis ‐, diexo ‐ or diendo ‐2,2′‐disubstituted quinazolinones 5a , 5b , 7a – f and 8 . diexo ‐Methylene‐bridged carboxamides 6a and 6b were treated “on water” with N ‐benzylpiperidinone ( 11 ) to afford spiropiperidine–quinazolinones 12a and 12b . All these reactions were performed at room temperature, without any catalyst or co‐solvent, and gave yields of up to 99 %.