Stereochemical Aspects of The 'tert-Amino Effect”: 2. Enantio- and Diastereoselectivity in the Synthesis of Quinolines, Pyrrolo[l,2-a]quinolines, and [l,4]oxazino[4,3-a]quinolines

摘要: Thermal isomerization of the optically pure 2-vinyl-N,N-dialkylanilines, with a methyl or an ethyl substituent (R2) at α-position N,N-dialkyl moiety, 4a (R1= H), 4b CH3), 5a and 6a (Rl= affords enantioselectively pyrrolo[l,2-α] quinolines 7a 7b [1,4]oxazino[4,3-a]quinoline 11, bridgehead carbon atom, quinoline 13, respectively. The optical purity these derivatives was determined by 1H NMR spectroscopy in presence chiral shift reagents. Heating analogues which R2is methoxymethyl group (4c 4d) refluxing 1-butanol yields, besides compounds 7c,d also regioisomers 8c,d 9c,d that are enantiomerically pure. Mixtures diastereomers 12a,b 14a,b were obtained cyclization compound 5b, 3-ethylmorpholinyl group, acyclic amine 6b, respectively, 1-butanol. 12a proven configuration 8, 9, 12, 14 X-ray analysis [(±)-12a] NOE difference spectroscopy. These results provide conclusive evidence for mechanism reactions, further examples “tert-amino effect”. effect substituents on enantio- diastereoselectivity is discussed.