Alkylation of Lithiated Imines

Reaction of 1, (R = H), with hexyl bromide and benzyl chloride 

Reaction of 1, R = CH, with bromoacetaldehyde diethylacetal (compare Normant H et al. (1976) Tetrahedron Lett 1379) 

Bromochloropropane (23.6 g, 0.15 mol) is added in one portion at — 10 °C to the solution of 1, whereupon the cooling bath is removed. The temperature rises over a few min to over 30 °C but is kept between 30 and 35 °C by occasional cooling (Note 2). After an additional 30 min (at 30-35 °C), the solution is cooled to 0 °C and 150 ml of ice water is added with vigorous stirring. The organic layer and three ethereal extracts are dried over potassium carbonate and subsequently concentrated under reduced pressure, keeping the bath temperature below 40 °C. This work-up should 

Reaction of 2 with butyl bromide and allyl bromide 

Butyl bromide (0.15 mol, 20.5 g) or allyl bromide (0.12 mol, 14.5 g) is added over a few seconds at — 30 and — 80 °C, respectively, whereupon the cooling bath is removed. In the reaction with C4H9Br the temperature rises over 10 min to 25 °C, the reaction with H2C=CHCH2Br is extremely fast as indicated by almost immediate disappearance of the yellow colour and a temperature rise to — 15 °C over a few s. The butylation is terminated by heating the solution for 30 min at 35 UC a faint yellow colour remains. The products are isolated as described under 1. The yields of the undistilled products are greater than 80%. For their conversion into the ketones see Exp. 5. 

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