5.4.4 Vilsmeier-Haack Reaction
Activated alkenes as well as aromatic compounds react with disubstituted formamides and POCl3 to give aldehydes (Scheme 7). The reaction is called Vilsmeier reaction.
Scheme 7
Mechansim
N,N -Dimethylformamide reacts with POCl3 to afford the reactive species that reacts with organic substrates to give the aldehydes (Scheme 8).
Scheme 8
Examples:
S. Hesse, G. Kirsch, Tetrahedron Lett. 2002 , 43 , 1213.
R. A. Aungst, Jr., C. Chan, R. L. Funk, Org. Lett. 2001 , 3 , 2611.
D. L. Comins, A. L. Williams, Org. Lett. 2001 , 3 , 3217.
5.4.5 Appel Reaction
Alcohols react with CCl4 or CBr4 in the presence of PPh3 to give alkyl halide (Scheme 9). The process is known as Appel reaction. The method is straight forward and the products are obtained in moderate to good yield.
Scheme 9