||Brønsted Acid/Silane Catalytic System for Intramolecular Hydroalkoxylation and Hydroamination of Unactivated Alkynes
Shibuya, Masatoshi ,
Fujita, Shoji ,
Abe, MasanoriYamamoto, Yoshihiko
2852 , 2017-04-07 , ACS Publications
The Brønsted acid-catalyzed intramolecular hydroalkoxylation and hydroamination of unactivated alkynes are described. We found that unactivated alkynes are electrophilically activated by a catalytic amount of bis(trifluoromethanesulfonyl)imide to undergo intramolecular hydroalkoxylation and hydroamination. In the presence of silane, the formed reactive exo-cyclic enol ether and exo-cyclic enamine intermediates are effectively reduced to the corresponding saturated cyclic ethers and N-protected cyclic amines. The 2,4-cis and 2,5-cis pyrrolidine derivatives are produced with high diastereoselectivity. Taking advantage of this selectivity, the 2,5-cis-disubstituted prolinol was also synthesized from glutamic acid in the optically active form.