Catalytic enantioselective construction of beta-quaternary carbons via a conjugate addition of cyanide to beta,beta-disubstituted alpha,beta-unsaturated carbonyl compounds.
The first general catalytic enantioselective conjugate addition of cyanide to beta,beta-disubstituted alpha,beta-unsaturated ketones and N-acylpyrroles was developed using a strontium catalyst derived from Sr(O(i)Pr)(2) and new chiral ligand 5. The reaction exhibited excellent enantioselectivity and a wide substrate scope using 0.5-10 mol % catalyst. 1,4-Adducts containing beta-quaternary carbons were exclusively produced over 1,2-adducts. ESI-MS analysis of the strontium catalyst indicated that the active catalyst was a trimetallic Sr/5 = 3:5 complex. The exclusive 1,4-selectivity was partly due to the ability of the strontium complex to promote both a retro-cyanation reaction from the 1,2-adducts and highly enantioselective conjugate cyanation.
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Yuta
Y
Tanaka
Motomu
M
Kanai
Masakatsu
M
Shibasaki
D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D007659:Ketones / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry; D013237:Stereoisomerism; D013379:Substrate Specificity
D007659:Ketones; D009570:Nitriles; D011758:Pyrroles; D002244:Carbon