Reduction of azetidin-2-ones 3-lactams

Diphenylsilane is compatible with the ester group at C-4 in azetidin-2-ones 203 and reduces only the amide carbonyl group affording azetidin-2-carboxylates 204 (Equation 55) 2004TL2193 . Removal of the / -methoxy-benzyl group from azetidin-2-carboxylates 204 allowed the preparation of conformationally strained amino ester hydrochlorides. 

Treatment of 4-(2-bromoalkyl)azetidin-2-ones 205 with L1AIH4 in diethyl ether yielded 2-(l-alkoxy-2-hydroxyethyl)-azetidines 206 and small amounts (1-5%) of r-4-(2-bromoalkyl)azetidines 81 (Equation 56) 20060L1101 . A 1,2-fission of the starting material followed by a nucleophilic substitution of bromide led toward the formation of these compounds. 1,4,4-Trisubstituted azetidin-2-ones 207 could be reduced to the corresponding azetidines 208 using lithium aluminium hydride in diethyl ether under reflux for 7-16h (Equation 57) 1996JOC6500 . 

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