Electrophilicities of 1,2‐Disubstituted Ethylenes

Abstract

The kinetics of the reactions of maleic anhydride, N‐methylmaleimide, fumaronitrile, diethyl fumarate, and diethyl maleate with pyridinium and sulfonium ylides were studied in DMSO at 20 °C. All of the reactions were found to follow a second‐order rate law, and can be described by the linear free energy relationship log k2 (20 °C) = sN(N + E), where N and sN are solvent‐dependent nucleophile‐specific parameters, and E is an electrophile‐specific parameter. The electrophilicity parameters E of the investigated acceptor‐substituted alkenes were derived from the linear correlations of (log k2)/sN vs. N, and range from –19.8 to –11.1.

Ethenesulfonyl Fluoride: The Most Perfect Michael Acceptor Ever Found?

“…[4] In line with the expectations based on Eq. (1), we obtained sultone 11 in almost quantitative yield when a mixture of 7 and dimedone (10) in DMSO was treated with triethylamine at ambient temperature for one hour (Scheme 4). Attempts to replace NEt 3 by a chiral base in order to generate 11 enantioselectively are presently under way.…”

“…The fluorosulfonyl-substituted ethylenes 1 and 7 are six and eight orders of magnitude more reactive than the corresponding phenylsulfonyl-and para-tolylsulfonyl-substituted ethylenes. [15] ESF (1) is also more electrophilic than trans-b,4-dinitrostyrene [16] and most 1,2-diacceptor-substituted ethylenes (except for maleic anhydride) [10] and can thus be considered to be one of the strongest Michael acceptors on our electrophilicity scale, noticeably exceeded only by ethylene derivatives with two acceptor groups at the same carbon atom. [6] To demonstrate the usability of this electrophilicity parameter for suggesting novel reactions, we studied the behavior of 1 towards the electron-rich arenes 8 (8 a-8 e).…”

“…(1) to derive the electrophilicity parameters E of acceptor-substituted ethylene derivatives from the second-order rate constants of their reactions with sulfonium (2) [7,8] and pyridinium ylides (3) [9] of known N and s N parameters. [10] Ylides 2 and 3 ( Table 1) were selected as reference nucleophiles for two reasons:1)The reactions of 2 and 3 with Michael acceptors proceed in as tepwise fashion, usually with rate-determining CÀCb ond formation to give zwitterions that rapidly cyclize to give stable products,a nd 2) the UV/Vis absorption of these ylides at l max > 315 nm enables the photometric monitoring of the progress of these reactions under pseudo-first-order conditions (with al arge excess of the Michael acceptor). They lides listed in Table 1 were now employed to determine the electrophilicity E of ESF (1).…”

“…Theresulting electrophilicity parameter E(7) = À16.63 shows that the introduction of ap henyl group in the b-position of ESF reduces the electrophilic reactivity by 4.5 orders of magnitude.T his is illustrated in Figure 4, which compares the electrophilicities of fluorosulfonyl-substituted ethylenes with those of other Michael acceptors.T he fluorosulfonyl-substituted ethylenes 1 and 7 are six and eight orders of magnitude more reactive than the corresponding phenylsulfonyl-and para-tolylsulfonyl-substituted ethylenes. [15] ESF (1)i sa lso more electrophilic than trans-b,4-dinitrostyrene [16] and most 1,2-diacceptor-substituted ethylenes (except for maleic anhydride) [10] and can thus be considered to be one of the strongest Michael acceptors on our electrophilicity scale,n oticeably exceeded only by ethylene derivatives with two acceptor groups at the same carbon atom. [6] To demonstrate the usability of this electrophilicity parameter for suggesting novel reactions,w es tudied the behavior of 1 towards the electron-rich arenes 8 (8a-8e).…”

Formation of diverse polycyclic spirooxindoles via three-component reaction of isoquinolinium salts, isatins and malononitrile

“…The most common reaction is 1,3-dipolar cycloaddition of cyclic nitrogen N -ylides such as pyridinium ylide with various electron-deficient acetylene and alkenes to give indolizine derivatives, in which the pyridyl ring is retained1920212223242526. The second widely used reaction is the reaction of cyclic nitrogen N -ylides with alkenes bearing electron-withdrawing groups to give the corresponding cyclopropanes, 2,3-dihydrofurans and other heterocyclic compounds, in which the pyridyl unit iseliminated2728293031323334. According to the structures of the substrates and the reaction conditions, the reaction of the cyclic nitrogen N -ylides showed very interesting molecular diversity263536373839.…”