22
S.C. Pan, B. List
Scheme 16. Catalytic asymmetric reductive amination of aldehydes using catalyst 9
We later developed an analogous enantioselective hydrogenation of
aldehydes to the corresponding β-branched alcohols using [RuCl 2
(xylyl-BINAP) (DPEN or DACH)] as the catalyst (Li and List 2007;
for an independent study, see Xie et al. 2007).
4
Iminium Catalysis
The in situ generation of an iminium ion from a carbonyl compound
lowers the LUMO energy of the system. Iminium catalysis is comparable to Brønsted- or Lewis acid activation of carbonyl compounds. The
LUMO energy is lowered, the α-CH acidity increases, and nucleophilic
additions including conjugate additions as well as pericyclic reactions
are facilitated (Eq. 34).
S.C. Pan, B. List
Scheme 16. Catalytic asymmetric reductive amination of aldehydes using catalyst 9
We later developed an analogous enantioselective hydrogenation of
aldehydes to the corresponding β-branched alcohols using [RuCl 2
(xylyl-BINAP) (DPEN or DACH)] as the catalyst (Li and List 2007;
for an independent study, see Xie et al. 2007).
4
Iminium Catalysis
The in situ generation of an iminium ion from a carbonyl compound
lowers the LUMO energy of the system. Iminium catalysis is comparable to Brønsted- or Lewis acid activation of carbonyl compounds. The
LUMO energy is lowered, the α-CH acidity increases, and nucleophilic
additions including conjugate additions as well as pericyclic reactions
are facilitated (Eq. 34).