Herein,
we report the development of a dual catalytic approach
for the cross-coupling of nitriles with aryl- and aliphatic-bromides.
A titanium(III) catalyst is used to activate nitriles enabling their
coupling with organobromides through a nickel catalyst. The Ni/Ti
system efficiently prepared unsymmetrical ketones with good chemoselectivity
and could selectively couple a bromide in the presence of other functionalizable
handles.
A modular titanium-promoted coupling of unsymmetrical internal alkynes with Weinreb amides is described. The coupling reaction takes place at room temperature and affords E-trisubstituted enones in moderate to good yields with high levels of regioselectivity. The system shows moderate chemoselectivity.
The organic cation in the title molecular salt, C5H13NCl+·Cl−, exhibits the gauche effect with a C—H bond of the C atom β to the chloro group donating electrons to the antibonding orbital of the C—Cl bond to stabilize the gauche conformation [Cl—C—C—C = −68.6 (6)°], as confirmed by DFT geometry optimizations that show a lengthening of the C—Cl bond relative to that of the anti conformation. Of further interest is the higher point group symmetry of the crystal (\overline{4}), compared that of the that of the molecular cation, which arises from a supramolecular head-to-tail square arrangement of four molecular cations that circulate in a counterclockwise direction when viewed down the tetragonal c axis.
Regioselective Synthesis of Enones via a Titanium-Promoted Coupling of Unsymmetrical Alkynes with Weinreb Amides. -In the presented enone synthesis a large scope of internal symmetric and asymmetric alkynes can be applied as substrates with good yields. The regioselectivity using unsymmetric alkynes depends strongly on the steric demand of the substituents. -(SILWAL, S.; RAHAIM*, R. J.; J. Org. Chem. 79 (2014) 17, 8469-8476, http://dx.
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