One-pot preparation of ethyl 2(Z)-4-(anilinoxy)-pentenoate by α-aminoxylation of propanal followed by Z-selective HWE reaction and the study on its cyclization reaction
A one-pot sequence of α-aminoxylation of n-propanal catalyzed by L-proline followed by the Z-selective Horner-Wadsworth-Emmons reaction was developed. The highly functionalized chiral γ-anilinoxy-Z-α,β-unsaturated ester 6 was obtained in 57-58% yield with 98:2 Z-selectivity from n-propanal in one-pot procedure. The transformation of the anilinoxy group of 6 into a hydroxyl group can be carried out by treatment with catalytic amount of CuSO4 in methanol to give either the corresponding alcohol 8 or chiral γ-valerolactone 4a in moderate yield. Chiral 6-methyl-2-phenyl-2H-1,2-oxazin-3(6H)-one 7 was obtained in 75% yield from 6 by treatment with CSA.
Kinetic resolution of racemic lactones by conjugate additions of allylic organolithium species: Direct formation of three contiguous centers with high diastereo- and enantioselectivities
(Matrix presented) Kinetic resolution of racemic α,β-unsaturated lactones by the organolithium species produced from asymmetric lithiation of N-Boc-N-(p-methoxyphenyl)cinnamylamine provides conjugate addition products with three contiguous stereogenic centers in yields of 62-77% with diastereomeric ratios from 75:25 to >99:1 and enantiomeric ratios for the major diastereomers from 94:6 to 98:2.
Lim, Sung H.,Beak, Peter
p. 2657 - 2660
(2007/10/03)
STUDIES ON STRUCTURALLY SIMPLE α,β-BUTENOLIDES. III. BEHAVIOUR OF (-)-(S)-δ-HETEROSUBSTITUTED γ-METHYL-α,β-BUTENOLIDES TOWARDS NUCLEOPHILES. PROTOANEMONIN AS INTERMEDIATE IN AN ELIMINATION-ADDITION MECHANISM.
The reactivity of the title compounds with different nucleophiles has been checked and it was shown that products from reaction with sodium phenylthiolate result from an elimination-addition process in which protoanemonin is the key intermediate.The synthesis of (-)-(R)-β-angelica lactone is reported for the first time.
Camps, P.,Cardellach, J.,Corbera, J.,Font, J.,Ortuno, R. M.,Ponsati, O.
p. 395 - 400
(2007/10/02)
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