Chiral primary-tertiary diamine-Brønsted acid salt catalyzed syn-selective cross-aldol reaction of aldehydes.
Highly syn-selective cross-aldol reaction of aldehydes has remained a challenging subject in the field of aminocatalysis. To achieve this end, chiral primary amines have been explored and the primary-tertiary diamine-Brønsted acid salts are found to promote the cross-aldol reactions of aldehydes with high activity and syn selectivity. Among various vicinal diamines screened, l-phenylalanine derived 2a/TfOH conjugate is identified as the optimal catalyst, showing good catalytic activity (up to 97% yield) and high syn selectivities (syn/anti up to 24:1, 87% ee). The current catalysis works selectively with small aliphatic aldehydes donors such as propionaldehyde and isobutyraldehyde, but not with aliphatic aldehydes bearing larger beta-substitute (>Me). In addition, the use of 2a/TfOH conjugate has also enabled the first syn-selective cross-aldol reactions of glycoaldehyde donors.
Beijing National Laboratory for Molecule Sciences (BNLMS), CAS Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 China.
Jiuyuan
J
Li
Niankai
N
Fu
Xin
X
Li
Sanzhong
S
Luo
Jin-Pei
JP
Cheng