One-Pot Intermolecular Reductive Cross-Coupling of Deactivated Aldehydes to Unsymmetrically 1,2-Disubstituted Alkenes

Abstract

The phospha-Peterson reaction between a lithiated secondary phosphane, MesP(Li)TMS, and an aldehyde affords Mes-phosphaalkenes which, upon methanol addition and P-oxidation, react with a second carbonyl compound site specifically to produce unsymmetric alkenes. The E/ Z selectivity of the one-pot cross coupling is largely determined by the electronic nature of the aryl substituent of the first aldehyde, with electron-donating groups giving rise to increased amounts of Z-alkenes.

Triphenylphosphaalkenes in Chemical Equilibria

“…As we could show in our adjusted protocol, this undesired reactivity can be overcome by using LiOEt as desilylating agent instead of MeLi. Thus, MesP(Li)TMS was prepared from MesP(TMS) 2 by treatment with one equivalent of LiOEt to afford MesP(Li)TMS which reacts smoothly at room temperature in Et 2 O with several aldehydes to afford Mes‐phosphaalkenes as the only products …”

“…We recently reported a modified protocol for the phospha ‐Peterson reaction, to synthesize P ‐Mes‐phosphaalkenes. Prior to our work, the starting material MesP(Li)TMS was made in situ by treating MesP(TMS) 2 with one equivalent of MeLi in THF .…”

Reactivity patterns of benzhydryl(mesityl)phosphane oxide – a potential intermediate in carbonyl-carbonyl coupling reactions?

“…These may include future work to decrease the steric demand of the P-substituent further, possibly together with an increase of oxygenation level of the P-center. [12,13] Experimental General experimental procedures. 1 H, 13 atmosphere.…”

“…[12,13] Experimental General experimental procedures. 1 H, 13 atmosphere. Compound 1 was prepared according to literature procedures.…”

“…Recently our group published a procedure which allows the formation of C ¼ C doubles bond by the direct coupling of two aldehydes (Figure 1a, b). [11][12][13] In contrast to the McMurry protocol [14] which uses low-valent transitional metals, requires harsh reaction conditions, and does not allow the selective preparation of unsymmetric alkenes from the coupling of two non-identical carbonyl compounds, our approach proceeds by a stepwise anionic mechanism which resolves the drawbacks mentioned above. In our synthetic methodology, [11] a first aldehyde reacts with a lithiated phosphanylphosphonate to obtain phosphaalkenes in which the C-center of the P ¼ C double bond exhibits an opposite polarization compared to that in the starting carbonyl compound (Figure 1b).…”