Electrophilic Reactivities of Azodicarboxylates

Abstract

The kinetics of the reactions of the azodicarboxylates 1 with the enamines 2 have been studied in CH(3)CN at 20 °C. The reactions follow a second-order rate law and can be described by the linear free energy relationship log k(2) (20 °C) = s(N+E) (E = electrophilicity parameter, N = nucleophilicity parameter, and s = nucleophile-specific slope parameter). With E parameters from -12.2 to -8.9, the electrophilic reactivities of 1 turned out to be comparable to those of α,β-unsaturated iminium ions, amino-substituted benzhydrylium ions, and ordinary Michael acceptors. While the E parameters of the azodicarboxylates 1 determined in this work also hold for their reactions with triarylphosphines, they cannot be used for estimating rate constants for their reactions with amines. Comparison of experimental and calculated rate constants for cycloadditions and ene reactions of azodicarboxylates provides information on the concertedness of these reactions.

Reactions of N1-Methyl-4-nitro-2,1,3-benzoselenadiazolium Tetrafluoroborate with Aliphatic and Cyclic Amines in Acetonitrile: Kinetic and Structure-Reactivity Correlations

“…Figure also reveals that the benzoselenadiazolium cation 1 displays an electrophilicity approximately 2.5–12.3 orders of magnitude less reactive that the other N‐electrophiles (i.e., di‐ter‐butyl azodicarboxylate 11 ( E = −12.23) , 4‐chlorobenzenediazonium 12 ( E = −6.70) , and 2,4‐dinitrobenzenediazonium tetrafluoroborate 13 ( E = −2.50) ) and 1.53 orders of magnitude more negative than that of 1,3,5‐trinitrobenzene 14 , the reference for the benzenoid electrophiles .…”

Electrophilicities of 1,2‐Disubstituted Ethylenes

“…The most reactive compound in this series of 1,2-disubstituted ethylenes, maleic anhydride (1a), has an electrophilic reactivity similar to that of diethyl azodicarboxylate, [27] benzylidene indandione, [28] or an acylazolium ion, [29] but it is less electrophilic than the gem-substituted bis(phenylsulfonyl)ethene. [30] The reactivity of the double bond decreases by approximately three orders of magnitude when the bridging oxygen in 1a is substituted by a methylimino group in N-methyl maleimide (1b), which has a reactivity similar to that of a palladium-stabilized 1,3-diarylallyl cation, [31] a 1,2-diaza-1,3-diene, [32] or β-nitrostyrene.…”

[4+2] Cycloadditions of Seven‐Membered‐Ring trans‐Alkenes: Decreasing Reactivity with Increasing Substitution of the Seven‐Membered Ring

“…The difference in reactions with DEAD compared to other dienes may arise because the mechanisms are different . Unlike concerted Diels–Alder reactions, the reaction between trans ‐alkene 12 and DEAD is expected to proceed by a stepwise mechanism through a zwitterionic intermediate . The nucleophilic trans double bond attacks the electrophilic nitrogen atom on DEAD, forming zwitterion 44 (Scheme ).…”

“…The regiochemistry of alkenes 46 and 47 was opposite of what was expected. Because these reactions likely proceed through stepwise mechanisms, bicyclic alkenes 15 and 17 should react similar to allylic silanes, forming a β‐silyl carbocation in the first step (Figure ) . Instead, reactions proceeded via an intermediate involving a tertiary γ‐silyl carbocation (Figure ), possibly because it is stabilized by the additional cycloalkyl group.…”