4721-98-6Relevant articles and documents
Synthesis of multi ring-fused 2-pyridones via an acyl-ketene imine cyclocondensation
Pemberton, Nils,Jakobsson, Lotta,Almqvist, Fredrik
, p. 935 - 938 (2006)
Polycyclic ring-fused 2-pyridones (5a-e and 9a-e) have been prepared via a microwave-assisted acyl-ketene imine cyclocondensation. Starting from 3,4-dihydroisoquinolines (4a-b) or 3,4-dihydroharman (8), fused 2-pyridones could be prepared in a one-step pr
Asymmetric Reduction of Cyclic Imines with Chiral Sodium Acyloxyborohydrides
Yamada, Koichiro,Takeda, Mikio,Iwakuma, Takeo
, p. 265 - 270 (2007/10/02)
Asymmetric reduction of prochiral cyclic imines with chiral sodium acyloxyborohydrides (5a-i), which are easily prepared by the reaction of NaBH4 with various N-acyl α-amino-acids, has been investigated.Of these new reducing agents, triacyloxyborohydrides (5c-f), derived from NaBH4 (1 equiv.) and (S)-N-acylproline (3 equiv.), were found to reduce 3,4-dihydropapaverine (2) in tetrahydrofuran to (S)-norlaudanosine (3) hydrochloride in 60percent optical yield.The N-benzyloxycarbonyl derivative (5c) could be isolated as a powder and characterized.The effect of solvents on this asymmetric reduction has been examined by the use of the isolated reagent (5c); halogenated alkane solvents such as CH2Cl2 or CHCl2CH3 gave a better optical yield of compound (3) (79percent e.e.).The reagent (5c) also reduced other cyclic imines (6a-c) and (8) to the corresponding alkaloids (7a-c) and (9) in excellent optical yields (70-86percent e.e.), providing an effective route to the asymmetric synthesis of these alkaloids.A possible reaction path for this reduction is also presented.
