Abstract
Lithium aluminium hydride (LAH) in tetrahydrofuran (THF) reacted rapidly with isoquinoline to give lithium tetrakis dihydroisoquinoline aluminate (LTDA). Proton and ('13)C NMR spectra indicated the presence of only 1,2- but not 1,4-dihydro isomer. Unlike isoquinoline, pyridine or quinoline was less reactive and gave the corresponding 1,2- as well as 1,4-dihydro ligands. In THF, the isoquinoline-LAH intermediate (LTDA) reacted with methyl iodide, ethyl bromide, n-propyl bromide, allyl bromide, n-butyl bromide and benzyl chloride but not sec- and tert-butyl bromides to give the corresponding 4-substituted isoquinolines. In diethyl ether (Et(,2)O), all of these alkyl halides reacted. The yields of products ranged from 25 to 64% in THF, and 43 to 61% in Et(,2)O. For most reactions, yields of alkylated products were substantially higher in Et(,2)O than in THF: a one-electron transfer mechanism was proposed. ('1)H NMR and mass spectra for the 4-substituted isoquinolines were reported. These reactions also gave other minor products including 1,2,3,4-tetrahydroisoquinoline, monoalkylated tetrahydroisoquinolines and dialkylated tetrahydroisoquinolines.
Trujillo, David Anthon (1983). Alkylations of isoquinoline via lithium aluminium hydride. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -548660.