A Nonoxidative Sequence for the Preparation of 1,2-Diketone Derivatives Using Aldehyde and Organometallic Building Blocks
作者:Gwyneth L. Pudner、Isabela Camp、Jonathan R. Scheerer
DOI:10.1021/acs.joc.2c00439
日期:2022.6.17
investigates a synthetic sequence for the preparation of 1,2-diketone products. The sequence avoids oxidative conditions and instead employs reliable transformations including the Horner–Wadsworth–Emmons and addition of Grignard reagents to N-methyl-N-methoxy (Weinreb) amide intermediates. The reaction sequence is suitable for the synthesis of nonsymmetric aliphatic and aryl substituted derivatives.
Eighteen phosphorus-based alkerrylation reagents 1a-6c were synthesized and condensed with n-butyraldehyde 7a and benzaldehyde 7f. They were condensed with the aldehydes 7b-e,g-n to produce 2-methoxy-2-alkenoates 8a-n and 2-phenoxy-2-alkenoates 9a-n. A discussion on different selectivities for the alkerrylation reagents under different experimental conditions (base, soh em, temperature), the influence of the aldehydes on the geometrical outcome (electron rich or poor substituents steric hindrance) and the selection of the most E-and Z-selective reaction conditions for each class of aldehydes are reported Namely, triphenyl phosphonium salt la at RT in THF with DBU was better for Z-selectivity while trifluoroethylphosphonates 5b, 6b and 6c at -78 degrees in THF with KN(SiMe3)(2) were better for E-selectivity. (C) 1997 Elsevier Science Ltd.