Triarylalkenes from the site-selective reductive cross-coupling of benzophenones and aldehydes

Abstract

PhP(Li)TMS converts benzophenones to phosphaalkenes which upon activation under oxidizing, basic conditions react with aromatic aldehydes under the formation of triarylalkenes.

Pd-Catalyzed Coupling of N-Tosylhydrazones with Benzylic Phosphates: Toward the Synthesis of Di- or Tri-Substituted Alkenes

“…13 4,4′-(2-Phenylethene-1,1-diyl)bis(fluorobenzene) (3c). 52 Column chromatography on silica gel afforded 61 mg of the desired compound (yield 70%), white solid, mp = 88−91 °C; R f = 0.5 (cyclohexane); 1 (1-(m-Tolyl)ethene-1,2-diyl)dibenzene (3d). 53 Column chromatography on silica gel afforded 74 mg of the desired compound (yield 91%), colorless oil, R f = 0.5 (cyclohexane); 1 (1-(4-Fluorophenyl)ethene-1,2-diyl)dibenzene (3e).…”

“…59 Column chromatography on silica gel afforded 52 mg of the desired compound (yield 52%), white solid, mp = 151−152 °C; TLC: R f = 0.5 (cyclohexane); 1 H NMR (300 MHz, CDCl 3 ): δ (ppm): 7.28 (d, J = 8.8 Hz, 2H), 7.15 (d, J = 8.6 Hz, 2H), 6.97 (s, 4H), 6.93−6.87 (m, 3H), 6.85 (d, J = 4.4 Hz, 2H), 3.86 (s, 3H), 3.83 (s, 3H), 2.29 (s, 3H); 13 (2-(4-Methoxyphenyl)ethene-1,1-diyl)dibenzene (3u). 52 Column chromatography on silica gel afforded 50 mg of the desired compound (yield 58%), colorless oil, R f = 0.5 (cyclohexane); 1 (2-(3-Chlorophenyl)ethene-1,1-diyl)dibenzene (3x). 61 Column chromatography on silica gel afforded 83 mg of the desired compound (yield 95%), colorless oil, R f = 0.5 (cyclohexane); 1 (2-(4-Chlorophenyl)ethene-1,1-diyl)dibenzene (3y).…”

The Fascinating World of Phosphanylphosphonates: From Acetylenic Phosphaalkenes to Reductive Aldehyde Couplings

“…Recent work has reported the coupling of ketones and benzaldehydes to trisubstituted alkenes by using PhP(TMS)Li as a coupling reagent. 57 All coupling protocols via phosphaalkene intermediates use inexpensive feedstock aldehydes directly in a one-pot reaction to form nonsymmetric alkenes. This is not the case in classic carbonyl olefination methods, such as the Wittig, HWE, Julia-Kocienski, and Peterson reactions, where multistep syntheses are required to prepare highly specific reagents.…”

[2 + 2] Cycloaddition of phosphaalkenes as a key step for the reductive coupling of diaryl ketones to tetraaryl olefins

“…Protocols that belong to the first group feature the attack of a carbon-based nucleophile at a carbonyl group to form the CC -bonds (Figure 1a), followed by an elimination step to establish the C=C bond. This category includes all of the classic carbonyl olefinations such as the Wittig, [5][6][7][8] Horner-Wadsworth-Emmons (HWE) 9 or Peterson reactions 10,11 as well as more contemporary approaches based on main group element reagents, [12][13][14][15][16] or catalyzed by transition metals. 17 With the exception of sporadic examples in the Peterson olefination, the nucleophilic attack pathway puts a limit on the substrate scope of these reactions, and tetra-substituted olefins remain largely elusive when using classic olefination protocols.…”