Cyclic nitronates from the diastereoselective addition of 1-trimethylsilyloxycyclohexene to nitroolefins. Starting materials for stereoselective Henry reactions and 1,3-dipolar cycloadditions

Induced by a stoichiometric excess of dichloro(diisopropoxy)-titanium, 1-trimethylsilyloxycyclohexene and (E)-nitroolefins (R—CH=CHNO 2 , R = C 6 H 5 , p-C 6 H 4 CH 3 , p-C 6 H 4 OCH 3 , p-C 6 H 4 CN, CH 3 ) combine in CH 2 Cl 2 solution at −90 °C preferentially with relative topicity ul, opposite to the corresponding reaction of enolates or enamines. The primary products are the epimeric bicyclic nitronates 4–6, which can be separated, and …