Reaction of 1-Azabicyclo[1.1.0]butane with Activated Amides

1-Azabicyclo[1.1.0]butane(ABB, 1) reacted with 3-acyl-1,3-thiazolidine-2-thiones (7,11a-m) in the presence of a catalytic amount of Mg(OTf) 2 to give the corresponding 2-(1-acylazetidin-3-yl)thio-1,3-thiazolines (8,12a-m).It was hypothesized that this reaction is primarily influenced by a steric bulkiness of acyl groups in 3-acyl-1,3-thiazolidine-2-thiones.Resulting compounds (8, 12k) were readily converted to thiols (13,14), and azetidine-3-thiol hydrochloride (15), which is the key intermediate of 1-(1,3-thiazolin-2-yl)azetidine-3-thiol hydrochloride (4) useful for the preparation of a new oral 1β-methylcarbapenem antibiotic L-084, was obtained quantitatively by hydrolysis of 14.