Copper(I)‐Catalyzed Wittig Olefination Reactions of N‐Tosylhydrazones with Trifluoromethylketones

Abstract

Cuprous iodide-catalyzed Wittig olefination reactions of N-tosylhydrazones with trifluoromethylketones are reported. This procedure provides an efficient method for the synthesis of various trifluoromethyl-substituted alkenes in moderate to good yields (up to 89 % yield) and good stereoselectivity (up to 93 % E-selectivity). To the best of our knowledge, it is the first report of a Wittig reaction of N-tosylhydrazones with ketones.

An Update of N-Tosylhydrazones: Versatile Reagents for Metal-Catalyzed and Metal-Free Coupling Reactions

“…Without the copper catalyst, the diazo intermediate generated in situ from N-tosylhydrazones was directly trapped by PPh 3 to afford the intermediates T41 for aza-Wittig olefination. They further affirmed that multifunctionalized alkenes could be delivered from the corresponding carbonyl compounds 71 and its alcohol precursors. 72 In 2015, Y.-Q.…”

One-Pot Multistep Synthesis of Trisubstituted Alkenes from N-Tosylhydrazones and Alcohols

“…This encouraged us to develop a one-pot multistep procedure for the synthesis of trisubstituted alkenes from N-tosylhydrazones and alcohols. In a continuation of our work on the development of new applications of N-tosylhydrazones, 8,9,11 herein, we report our successful attempt to achieve this goal (Scheme 1).…”

“…But the two reported methods can only be used to synthesize disubstituted alkenes. Recently (Scheme 1), we reported the copper(II) acetylacetonate catalyzed Wittig reaction of ketone-derived tosylhydrazones with aldehydes 8 and copper(I) iodide catalyzed Wittig reaction of tosylhydrazones with trifluoromethyl ketones, 9 from which various trisubstituted alkenes were obtained in good yields and good E-selectivity. However, the starting materials of all these procedures are limited to carbonyl compounds, the direct use of alcohols as starting substance has not been developed.…”

“…However, the starting materials of all these procedures are limited to carbonyl compounds, the direct use of alcohols as starting substance has not been developed. For example, in our reported copper(I) iodide catalyzed Wittig reaction of tosylhydrazones with trifluoromethyl ketones, 9 the trifluoromethyl ketones were prepared from the addition of trimethyl(trifluoromethyl)silane to aldehydes, followed by oxidation using Dess-Martin reagent. A large excess of the Dess-Martin reagent was used and we need to isolate the trifluoromethyl ketones in a pure form.…”

Decarbonylative Olefination of Aldehydes to Alkenes

“…The carbonyl olefination of ketones or aldehydes by phosphorous ylids, discovered by Wittig (Scheme 1a), has been a cornerstone of modern synthesis due to its utility and reliability. [1][2] However, the utility of the chemistry is hindered by the need to pre-form phosphorous ylids and the production of stoichiometric waste, necessitating the development of more atom-economical alternatives. Recently we reported the high activity of heterogeneous catalysts based on Pd-doped hydrotalcites (Pd-HTs) for selective decarbonylation of aldehydes.…”