Seven membered ring chelates derived from γ-hydroxyamides and triphenyltin or diphenylboron

N-Benzyl-4-hydroxy-butyramide (1), 4-hydroxy-N-[(R)-1-phenyl-ethyl]-butyramide (2), and (R)-4-hydroxy-2-methyl-N-[(R)-1-phenyl-ethyl]-butyramide (3a) were used to prepare new diphenylboron and triphenyltinoxy compounds: diphenylborinic acid 3-benzylcarbamoyl-propyl ester (4), diphenylborinic acid 3-[(R)-1-phenyl-ethylcarbamoyl]-propyl ester (5) and diphenylborinic acid (R)-3-[(R)-1-phenyl-ethylcarbamoyl]-butyl ester (6), N-benzyl-4-triphenyltinoxy-butyramide (7), 4-triphenyltinoxy-N-[(R)-1-phenyl-ethyl]-butyramide (8), and (R)-4-triphenyltinoxy-2-methyl-N-[(R)-1-phenyl-ethyl]-butyramide (9). The X-ray diffraction analysis of a crystalline structure of the new γ-hydroxyamide 3a is reported, as well as that of the first example of a crystalline structure where a diphenylborinic ester forms a seven membered chelate, by a carbonyl coordination to boron (4). Structural studies of tin and boron esters were performed by NMR. The Cdouble bond; length as m-dashO internal coordination to tin atoms, affording seven membered rings, was observed by 119Sn NMR experiments at low temperature.