Syntheses of tetrahydrofurans via asymmetric electrophilic addition reactions

Abstract

Syntheses of chiral electrophilic reagents were studied. N-Iodo electrophilic reagents were prepared from L-tartaric acid. Intra- and inter- molecular electrophilic reactions using these reagents showed little enantioselectivity. Next we intended to secure chiral pyridine or ether type ligands which can make complexes with $I_2$. The reaction using these complexes gave low enantioselectivity. Using mercury(II) cation as an electrophile and salen as a chiral ligand, many electrophilic reactions were performed. With salen 41 and substrate 19, 73% ee was obtained. Finally we attempted to generate chiral electrophiles using transition metal complexes. In the case of NIS as a source of electrophile, (R)-BINOL-Ti(IV) complex seemed to form chiral electrophiles. Several reactions using this complex afforded interesting results that chirality from chiral ligands could be transferred to substrates.