Asymmetric synthesis of 2,6-substituted dihydropyrone catalyzed by 3-monosubstituted and 3,3′-bisubstituted BINOL titanium complexes

✍ Scribed by Hong Yu; Ji Zhang; Yuan-Cong Zhao; Na Wang; Qin Wang; Xin-Bin Yang; Xiao-Qi Yu

• Book ID: 111491124
• Publisher: Versita
• Year: 2008
• Tongue: English
• Weight: 194 KB
• Volume: 62
• Category: Article
• ISSN: 0366-6352
• DOI: 10.2478/s11696-008-0010-6

✦ Synopsis

Abstract

Asymmetric hetero-Diels-Alder (HDA) reactions of aromatic aldehydes with Danishefsky’s diene derivative were carried out smoothly in the presence of the Ti(IV)-(R)-BINOL (1:1.2) complex to give the corresponding chiral 2,6-disubstituted dihydropyrones under mild conditions. The readily accessible I-Ti(OCH(CH3)2)4 (1.2:1) complex was found to be an effective catalyst for this reaction. Aromatic aldehydes afforded the corresponding products in moderate yields (up to 72 %) with good enantioselectivities (up to 80 % ee). Aromatic aldehydes in presence of the TiCl4-NaOCH3-II (1:4.2:1.2) complex gave the products in higher yields (up to 73 %) with better enantioseletivities (up to 84 % ee).