Synthesis and Reactions of a-Bromo-N-alkoxyimidates
The reaction of alkyl hydroxamates 2 with (C2H5)3O · BF4 in CH2Cl2 affords N-alkoxyimidates 3. The direct alkylation of hydroxamic acids 1 with 1,2-dibromoethane gives the 5,6-dihydro-1,4,2-dioxazine derivatives 4. The reactions of the acyclic imidates 3 as well as the cyclic N-alkoxyimidates 4 with N-bromosuccinimide in CCl4 produces the α-bromoimidates 5a–d and 6a–d. The α-bromine atom in the bromides 5b, d and 6a, b, d can be displaced by fluorine and azido substituents to yield the α-fluoro-N-alkoxyimidates 7b, d and 10a, b, d and the α-azido compounds 8b, d and 11a, b, d, respectively. The reduction of the azides 8b, d and 11a, b, d affords the α-aminoimidates 9b, d and 12ab, d, respectively. The reaction of the bromides 6a–d with benzene derivatives 14a–d in the presence of AgBF4 affords the aromatic substitution products 15a–d. Acid-catalyzed hydrolysis of 15a, c gives the arylsubstituted carboxylic acids 16 and 17.