Pushing the boundaries of vinylogous reactivity: catalytic enantioselective mukaiyama aldol reactions of highly unsaturated 2-silyloxyindoles.
The first example of catalytic, enantioselective hypervinylogous Mukaiyama aldol reaction (HVMAR) involving multiply unsaturated 2-silyloxyindoles is reported. The reaction utilizes a chiral Lewis base-catalyzed Lewis acid-mediated technology to deliver homoallylic 3-polyenylidene 2-oxindoles with extraordinary levels of regio-, enantio-, and geometrical selectivity. This work highlights a subtle yet decisive influence of the indole N-substituents on the propagation of the vinylogous reactivity space of the donor substrates up to ten bonds away from the origin of the vinylogy effect. Analysis of the (13) C NMR chemical shifts of the C-ω remote site within homologous silyloxyindole donors enabled rationalization of the results and easy qualitative prediction of the HVMAR reactivity/inertia toward a given aldehyde acceptor.
Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27 A, 43124 Parma (Italy), Fax: (+39) 0521-905006. claudio.curti@unipr.it.
Claudio
C
Curti
Andrea
A
Sartori
Lucia
L
Battistini
Nicoletta
N
Brindani
Gloria
G
Rassu
Giorgio
G
Pelosi
Alessio
A
Lodola
Marco
M
Mor
Giovanni
G
Casiraghi
Franca
F
Zanardi
aldol reaction; amides; asymmetric synthesis; oxindoles; vinylogy