The preparation and transformations of 2-aza-3-oxabicyclo [2.2.1] heptene hydrochloride

Reaction of 1- chloro 1- nitroso cyclohexane with excess freshly prepared cyclopentadiene in ether: ethanol gives the crystalline 2-aza 3 oxabicyclo (2.2.1) heptene hydrochloride (1) in 89%, yields. 2-Aza 3-oxabicyclo (2.2.1) heptene (2), generated in situ with pyridine can be acylated with a variety of acid chlorides and anhydrides, thus providing a novel and convenient route to diverse oxazabicycloheptenes. The free base 2 generated with NaHCO₃ in a two phase system, readily reacts with formalin leading to the Mannich base adduct 16, with PhNCS to the thiourea 19 and with i-AmONO to the nitroso compound 20. PGG → PGE type cleavage is observed on reaction of the in situ generated 2 with excess benzoylchloride, MsCl and TsCl. Surprisingly, the reaction of 1 with ArCHO in presence of pyridine gives N-α-chloroaryl compounds possessing a highly reactive halogen. Diimide reduction of 2 gives the parent oxazabicycloheptane system-related to PG-endoperoxides—which was characterized as the hydrochloride or the benzoyl derivative.