Gold(I)-Catalyzed Synthesis of Optically Active 1,4-Oxazepan-7-ones

Abstract

Optically active seven-membered lactones, dimethyleneoxazepanones, were readily prepared in good yields from chiral β-(N-propargylic)amino-α-methylene carboxylic acid tert-butyl esters in the presence of catalytic amounts of Ph3PAuCl and Cu(OTf)2. A smooth 7-exo-dig cyclization was observed.

A mechanistic study on the SHi reaction at tin atoms in a radical cascade reaction

“…Compound 1a was prepared using a previously reported method. 11 We checked the role of the ester group in the cascade reaction. We examined the reaction of compound 1b, which was prepared by the reduction of ester 1a, under the same conditions.…”

“…The reaction of 1c, prepared from the corresponding tertbutyl ester, 11 and 4a was examined under the same conditions as the radical cascade process. Thus, a mixture of 1c and 4a in toluene at a concentration of 10 −2 M was stirred at room temperature.…”

“…(3S,3aS)-tert-butyl 5,5-dibutyl-3-phenyl-2-tosyl-1,2,3,3a,4,5hexahydrostannolo [3,4-c]-pyrrole-3a-carboxylate (301.2 mg, 0.51 mmol), which was prepared by the reported method, 11 was dissolved in CH 2 Cl 2 (20 mL) and TBSOTf (202.7 mg, 0.77 mmol) and 2,6-lutidine (0.09 mL, 0.77 mmol) was added to the solution. The reaction mixture was stirred for 24 h at room temperature.…”