The addition of a dialkyl acetylenedicarboxylate to 3-chloroindole-2-carboxaldehyde in the presence of triphenylphosphine leads initially to a vinylphosphonium salt, which undergoes an intramolecular Wittig reaction to produce the title compounds in fairly good yields.
WebbJ.S., CosulichD. B., MowatJ. H., PatrickJ. B., BroschardR. W., MeyerW. E., WilliamsR. P., WolfC. F., FulmorW., PidacksC., LancasterJ. E., and LancasterJ. E., J. Am. Chem. Soc.84, 3187 (1962).
2.
AllenG.R.Jr., PollettoJ. F., and WeissM. J., J. Am. Chem. Soc., 86, 3877 (1964).
3.
AllenG.R.Jr., and WeissM. J., J. Org. Chem.30, 2904 (1965).
4.
SchweizerE.E., and LightK. K., J. Org. Chem., 31, 870 (1966).
5.
ZieglerF.E., and JeroncicL. O., J. Org. Chem.56, 3479 (1991).
6.
RainesS., ChaiS. Y., and PalopoliF. P., J. Org. Chem.36, 3992 (1971).
7.
MajoV., and PerumalP. T., J. Org. Chem.61, 6523 (1996).
8.
FranckR.W., and BernadyK. F., J. Org. Chem.33, 3050 (1968).