Hydroboration of 1-allyl-1,2,3,4-tetrahydroquinoline

Hydroboration of 1-allyl-1,2,3,4-tetrahydroquinoline (I) with triethylamine-borane in the molar ratio 1 : 1 afforded a product from which 6,7-benzo-5-aza-1-boraspiro[4,5]decane (II) was isolated. Ethanolysis of II gave diethyl 3-(1,2,3,4-tetrahydro-1-quinolyl)propylboronate (III). Acid hydrolysis of the crude hydroboration product and subsequent oxidation with alkaline hydrogen peroxide led to a mixture of 3-(1,2,3,4-tetrahydro-1-quinolyl)-1-propanol (IV), 1,2,3,4-tetrahydroquinoline (V) and 1-propyl-1,2,3,4-tetrahydroquinoline (VI). Hydroboration of I with triethylamine-borane in the molar ratio 3 : 1, followed by oxidation, gave a mixture of IV, V, VI and 1-(1,2,3,4-tetrahydro-1-quinolyl)-2-propanol (VIII). Hydroboration of I with diborane in situ in diethylene glycol dimethyl ether at 20 °C and subsequent acid hydrolysis and oxidation with alkaline hydrogen peroxide afforded a mixture of IV, V and VIII when the hydroboration product was first heated to 150 °C and then subjected to the above-mentioned processing, only compounds IVand V were formed.