A base-mediated synthesis of N-hydroxy- and N-alkoxyindoles from 2-nitrostyrenes.

Sequential treatment of alkyl 2-(2-nitroaryl)-2-butenoates with potassium tert-butoxide and an electrophile, such as methyl iodide, benzyl bromide and allyl bromide, afforded N-alkoxyindoles. In related reactions, using sodium tert-pentoxide as the base with or without in situ addition of an electrophile afforded N-alkoxy- and N-hydroxyindoles, respectively. Electrophiles such as dimethylsulfate, p-tosyl chloride, and acetic anhydride afforded moderate yields of the respective N-methoxy-, N-tosyloxy, and N-acetoxyindoles, while methyl iodide, benzyl bromide, and 1-bromohexane failed to form alkylated products using sodium tert-pentoxide as the base.

Palladium-Catalyzed Double Reductive Cyclization of 2,3-Dinitro-1,4-dialkenylbenzenes. Synthesis of 1H,8H-Pyrrolo[3,2-g]indoles.

A flexible route to both symmetrical and unsymmetrical 1H,8H-pyrrolo[3,2-g]indole has been developed. The key and ultimate step is a double palladium-catalyzed, carbon monoxide mediated reductive cyclization of 1,4-dialkenyl-2,3-dinitrobenzenes. The cyclization precursors were prepared by a double Kosugi-Migita-Stille cross coupling of 1,4-dibromo-2,3-dinitrobenzene with an alkenyltin reagent to give symmetrical products. Unsymetrical cyclization precursors were prepared by two sequential cross couplings using 4-iodo-2,3-dinitrophenyl trifluoromethanesulfonate as the starting material.