Base- and acid-catalyzed intramolecular oxy-Michael reaction for the synthesis of tetrahydrofuran ring

作者：Murata Yuki; Uenishi Jun'ichi^*

来源：Tetrahedron, 2016, 72(32): 4962-4967.

DOI：10.1016/j.tet.2016.06.081

• Oxy-Michael reaction
• Stereochemistry
• THF ring
• Facial selectivity
• Catalytic reaction

Base- and acid-catalyzed intramolecular oxy-Michael reactions are reported. Three e-hydroxy alpha,beta-unsaturated ketones 1, 2, and 3 and one ester 4 were cyclized in 5-exo-trigonal fashion to afford 2,5disubstituted tetrahydrofurans in good yields. The substituent at the gamma-hydroxy group and its stereo chemistry influenced the stereoselectivity of the THF products. The precursor 2 bearing an (R)-gamma-hydroxy group gave 2,5-trans-6 exclusively. In contrast, 3, bearing an (S)-gamma-hydroxy group, gave only 2,5-cis-7 under acidic conditions but gave a mixture of 2,5-trans and 2,5-cis isomers of 7 under basic conditions. On the other hand, in the absence of a hydroxyl group at the gamma-position, the cyclization conducted under both basic and acidic reaction conditions provided a mixture of 2,5-trans- and 2,5-cis isomers of 5 and 8.

• 出版日期2016-8-11