The Chemistry of α'-Trifluoroacetamido α-Diazoketones

Abstract

2-Amino-8-methoxy-l,2,3,4-tetrahydro-2-naphthoic acid hydrochloride (6) was converted into its trifluoroacetamide (8) and the reaction of its 1,3-oxazolone (7) with diazomethane studied. The major product from this reaction was shown to be the α'-trifluoroacetamido α-diazoketone (11), the minor products were identified as the 1,3-oxazine (14) and the 1,3-oxazepine (13). The acid-catalysed cyclization of the diazoketone (11) provided a dienone (16) in modest yield. The route to key substrates for the synthesis of gibberellins with potential C13 nitrogen functions was thus demonstrated. The reaction of two other oxazolones (25) and (28) and a pseudo-oxazolone (17) with diazomethane was investigated and the necessity for a strong electron-withdrawing group attached to the oxazolone ring demonstrated. The photochemical Wolff rearrangement of diazoketone (20) provided a homologated phenylalanine derivative (21). The reaction of an indanyloxazolone (25) with diazomethane furnished the corresponding diazoketone (26) in high yield.