46255-79-2Relevant academic research and scientific papers
Stereoselective deprotonation of tropinone and reactions of tropinone lithium enolate
Majewski, Marek,Zheng, Guo-Zhu
, p. 2618 - 2626 (2007/10/02)
Tropinone (6) was deprotonated with lithium diisopropylamide and with chiral lithium amides (18-24) and the resulting enolates (two enantiomers) were treated with electrophiles.The aldol reaction with benzaldehyde and deuteration were both diastereoselective.The former yielded only one isomer (exo, anti) of the aldol 8a; the latter proceeded from the exo face.This selectivity permitted us to probe the deprotonation of tropinone with lithium amides; it was concluded that the reaction involves predominantly the exo axial protons.The reaction of tropinone enolate with ethyl chloroformate led, via a ring opening, to the cycloheptenone derivative 9.The reaction with methyl cyanoformate yielded, in the presence of silver acetate and acetic acid, the β-ketoester 8b; however, in the absence of these additives, and especially when 12-crown-4 was added to the enolate, a ring opening leading to the pyrrolidine derivative 10 occured instead.Deprotonation of tropinone with chiral amides proceeded with modest enantioselectivity.A synthesis of non-racemic anhydroecgonine via this strategy allowed establishing the absolute stereochemistry of deprotonation.
