Group 14 organometallic reagents. 8. Organotin-mediated synthesis of macrocyclic tetraesters: regio- and stereochemistry

The reaction of 4-phenyl- and 4-methyl-substituted dioxastannolanes I (R = Ph, Me) with glutaryl chloride has been investigated to provide a clear description of the regio- and stereochem. of the organotin-mediated synthesis of macrocyclic tetraesters. In contrast with previous reports, the reaction does not exhibit the described regio- and stereospecificity, affording all possible isomers in substantial amts., in line with the expected product distribution for a thermodynamically controlled reaction. The regioisomeric preference, obsd. to some extent for the Ph derivs., appears to be unpredictably dependent on the substituent nature. Although exptl. conditions can be optimized for reasonable yields of dimeric tetraester, the regio- and stereochem. outcome of this reaction can hardly be predicted.