N‑Heterocyclic Carbene/Lewis Acid Dual Catalysis for the Divergent Construction of Enantiopure Bridged Lactones and Fused Indenes

• Published in: Journal of organic chemistry Vol. 81; no. 23; pp. 11871 - 11881
• Main Authors: Wang, Zhan-Yong, Ding, Ya-Li, Li, Shi-Ning, Cheng, Ying
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 02.12.2016; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Physical Sciences; Science & Technology; COOPERATIVE CATALYSIS; ASYMMETRIC-SYNTHESIS; LEWIS-ACID; STRATEGY; GAMMA-LACTAMS; 2-AROYLVINYLCINNAMALDEHYDES; SELECTIVE SYNTHESIS; STEREOSELECTIVE-SYNTHESIS; PODOPHYLLUM LIGNANS; DERIVATIVES
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/acs.joc.6b02329

The chiral triazole carbene and Ti­(OPr-i)4 cocatalyzed reaction between α,β-unsaturated aldehydes and 2-(aroylvinyl)­benzaldehydes was systematically studied. A divergence in reaction pathways was observed under different reaction conditions. In benzene solvent and at ambient temperature, the reaction produced 4,5-dihydro-1,4-methanobenzo­[c]­oxepin-3-ones, the bridged caprolactones, as the major products in moderate yields with excellent enantioselectivity. The same reaction in dichloroethane and at 50 °C, however, gave 2,8-dihydrocyclopenta­[a]­indenes as the major products in most cases. The application of the method developed was demonstrated by the transformation of the bridged lactone products into enantiopure 4-hydroxy-1,2,3,4-tetrahydronaphthalene-2-carboxylic acids.