Reaction of benzoxasilocines with aromatic aldehydes: Synthesis of homopterocarpans

• Míriam Álvarez-Corral,
• Cristóbal López-Sánchez,
• Leticia Jiménez-González,
• Antonio Rosales,
• Manuel Muñoz-Dorado and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2007, 3, No. 5, doi:10.1186/1860-5397-3-5

• diastereochemical outcome of the reaction, as observed before with the benzoxasilepines, [4] a selection of benzaldehydes with strongly (OMe) or weakly (OPiv) electron donating groups in ortho, meta and para positions were assayed (Table 1). Under the same experimental conditions used for the preparation of

• . When the reaction is performed in CHCl3, a slight increase in the yields is observed, but the diastereoselection levels are basically the same. We have also described that benzoxasilepines can be condensed with benzaldehydes in the presence of a stoichiometric amount of KF and 18-crown-6 and a

• . Reagents: i CH2 = CHCH2SiMe2Cl, Et3N, DCM, 85%; ii 2nd generation Grubbs catalyst, DCM, 91%. Reagents: i: BF3·Et2O (1 eq), MeOH 95%; ii: substituted benzaldehydes, BF3·Et2O (1 eq), DCM; iii: substituted benzaldehydes, BF3·Et2O (2 eq), DCM; see Table 1 for cis/trans ratios and yields. Reagents: i: a) OsO4