1 3
Topics in Current Chemistry (2019) 377:38
(Scheme 10). Shortly after, Kirsch et al. [46] disclosed the direct carbocyclization
of aldehydes with alkynes by a combined gold and amine catalysts system. Interestingly, by altering the amine catalyst employed, the generation of the final product
could be controlled, providing either product 48 or 49. Product 48 proceeds through
H
O
Ph
NH 2
O
N
Ph
O
AgOTf (10 mol%)
Proline 4 (10 mol%)
41
42
43
44
91% yield
+
ethanol, 50-60
o
C
Scheme 10 Multicomponent reaction providing the cyclic product 44
[(Ph 3 PAu) 3 O]BF 4 (10 mol%)
48, R = H
82% yield
6–18 h, 70
o
C, CDCl 3
R
CO 2 Me
MeO 2 C
O
H
CO 2 Me
MeO 2 C
H
O
CO 2 Me
MeO 2 C
H
O
N
H
N
H
45
46
47
49, R = Me
71% yield
Cu(OTf) 2 (6 mol%), Dioxane
20–30
o
C, 2-14 days
Ar = 3,5-tBu-4-MeOC 6 H 2
R
CO 2 Me
MeO 2 C
O
H
45
CO 2 Me
MeO 2 C
H
O R
52a R = Et, 59 yield, 72 ee
52b R = Me, 47 yield, 41% ee
52c R = n-Bu, 65% yield, 77% ee
52d R = Ph, 66 yield, 36% ee
MeO
MeO
PAr 2
PAr 2
50 (15 mol%)
NH 2
51 (10 mo%)
Scheme  11 Selected examples from the direct α-functionalization of aldehydes and alkynes, and the
enantioselective version of the chemical transformation
Reprinted from the journal
9