Stereoselective Synthesis of (2E,4Z)‐Dienamides Employing (Triphenylphosphoranylidene)ketene

Abstract

The three-component reaction between ylide Ph 3 PCCO, amines and aldehydes is known to afford selectively (E)-α,β-unsaturated amides. We applied a variant of this methodology to the preparation of (2E,4Z)-dienamides 11 utilizing the phosphonium salt formation from ethyl 5-aminopentanoate hydrochloride and Ph 3 PCCO followed by deprotonation with DBU and a Wittig olefination of the corresponding ylide with

Essential structural features of (2Z,4E)-5-phenylpenta-2,4-dienoic acid for inhibition of root gravitropism

“…After being stirred for 2 h at room temperature, the mixture was filtered using celite and the filtrate was evaporated to afford the crude product (44.7 mg) of (Z)-3-phenyl-2-propenal as colorless oil (Z:E = 20:1): 1 H-NMR (270 MHz,CDCl 3 ) δ: 6.20 (dd, J = 11.5, 8.1 Hz, 1H), 7.38-7.45 (m, 5H), 7.63 (d, J = 11.5 Hz, 1H), 9.97 (d, J = 8.1 Hz, 1H). The spectral data were consistent with those reported in the literature (Pachali et al, 2009). The aldehyde was used in the next reactions without further purification.…”

Preparation of conjugated dienoates with Bestmann ylide: Towards the synthesis of zampanolide and dactylolide using a facile linchpin approach

“…The study of the reactions between Bestmann ylide, alcohols and α,β-unsaturated aldehydes began with the investigation of the coupling between linchpin 1 [ 46 ], E -hex-2-en-1-ol ( 9a ) and E -cinnamaldehyde ( 10a ) ( Table 1 , entry 1). Typically, Bestmann ylide reactions are performed at elevated temperature in a high boiling and/or ether solvent, such as toluene, 1,4-dioxane or THF [ 11 , 14 – 17 19 – 20 ]. To investigate the necessity for high temperature, the primary reaction in this study was initiated at room temperature (19 °C) in toluene and then progressively warmed to reflux (110 °C) while monitoring the progress by TLC.…”

“…Its utility was subsequently explored, with pioneering work by Bestmann and co-workers [ 3 – 5 ] lending the name Bestmann ylide to this versatile and readily obtained reagent [ 6 – 8 ]. Studies revealed that the ylide readily reacts with alcohols and amines to form α-phosphoranylidene esters or amides, providing diverse isolable Wittig reagents that can be used in subsequent transformations [ 4 – 5 9 – 11 ]. Furthermore, if the α-phosphoranylidene ester or amide is formed in the presence of an aldehyde, ketone or ester, an additional in situ Wittig reaction can occur [ 12 – 18 ].…”

“…Although the utility of the Bestmann ylide in the synthesis of acyclic α,β-unsaturated esters and dienamides has already been reported [ 11 , 13 , 16 ], its application to the synthesis of α,β,γ,δ-unsaturated esters (i.e., dienoates) remains uncharted. In this paper, a three-component reaction between α,β-unsaturated aldehydes, alcohols and the Bestmann ylide is described.…”