Formation and HERON Reactivity of Cyclic N,N-Dialkoxyamides

Abstract

Cyclic N,N-dialkoxyamides have been made, for the first time, by hypervalent iodine oxidation of β- and γ-hydroxyhydroxamic esters 17, 19, and 21. The fused γ-lactam products, N-butoxy- and N-benzyloxybenzisoxazolones (22a and 22b), are stable while alicyclic γ-lactam and δ-lactam products, 24 and 25, although observable by NMR spectroscopy and ESI-MS are unstable at room temperature, undergoing HERON reactions. The γ-lactam 24 undergoes exclusive ring opening to give a butyl ester-functionalised alkoxynitrene 28. The δ-lactam 25, instead, undergoes a HERON ring contraction to give butyrolactone (27). The structures of model γ- and δ-lactams 6, 7, and 8 have been determined at the B3LYP/6-31G(d) level of theory and the γ-lactams are much more twisted than the acyclic N,N-dimethoxyacetamide (5) resulting in a computed amidicity for 6 of only 25 % that of N,N-dimethylacetamide (3). The HERON reactions of N,N-dimethoxyacetamide (5) and alicyclic models 6 and 8 have been modelled computationally. The facile ring opening of 6 (EA = 113 kJ mol–1) and ring contraction of 8 (EA = 145 kJ mol–1) are predicted well, when compared with the HERON rearrangement of 5 (EA = 178 kJ mol–1).

Experimental and theoretical studies of the nanostructured {Fe3O4@SiO2@(CH2)3Im}C(CN)3catalyst for 2-amino-3-cyanopyridine preparationviaan anomeric based oxidation

“…The proposed mechanism for the in-situ oxidation-reduction in Cannizzaro reaction through unusual hydride transfer viaanomericeffect [37] In a proposed mechanism, as portrayed in Scheme 7. the cationic site of the {Fe 3 O 4 @SiO 2 @(CH 2 ) 3 Im}C(CN) 3 plays a crucial role in activating of aromatic aldehydes and acetophenones as electrophile species and also at the same time the anionic site of the catalyst could interact with acidic hydrogen in malononitrile to trigger nucleophilic addition. Afterward, the reaction moves forward via the interaction between enamine 2 (generated from the reaction of ketone and ammonium acetate) and alkylidene malononitrile 3 (generated from the reaction of aldehyde and malononitrle) to yield the corresponding intermediate [38]. In Table 4 have shown the selected structural data (bond length (Å), bond angle (°) and torsional angle (°)) of the precursors (intermediate 7; R-and S-isomers), the transition states (with different orientations), intermediate and the product.…”

Heteroatom Substitution at Amide Nitrogen—Resonance Reduction and HERON Reactions of Anomeric Amides

“…We named this class ‘anomeric amides’ on account of the pronounced anomeric effects that can and do occur between the heteroatoms [26,27,28,29,30,31,32,33,34,35]. However, the physical, theoretical, and chemical properties of various congeners differ from those of conventional primary, secondary, and tertiary alkylamides.…”

“…We have also encountered several anomeric reactive intermediates through reactions of N -acyloxy- N -alkoxyamides: reaction of 2b with base generates N -alkoxy- N -hydroxamate anions 2g [45] and reaction with azide ultimately generates 1-acyl-1-alkoxydiazenes, which are aminonitrenes 2h [53,54]. We have generated N , N -dialkoxyamides 2c in related studies by solvolysis of N -alkoxy- N -chloroamides 2a in aqueous alcohols and through the reaction of hydroxamic esters with hypervalent iodine reagents in appropriate alcohols [30,55,56]. Other anomeric amides of theoretical interest to us are N -amino- N -chloroamides 2f [34], as well as N -amino- N -thioalkylamides 2i and N -chloro- N -thioalkyamides 2j .…”

Pyrolysis of hydrazine derivatives and related compounds with N N single bonds

“…The dialkylamino radicals, formed either thermally or photochemically in solution, can be used as initiators for radical polymerization [177] The reaction of the dimethylamino radical with toluene and substituted toluenes yielded a Hammett value of -1.08 for the abstraction reaction giving R 2 NH and a deuterium isotope effect of 4.0. The rate of the thermal decomposition of tetramethyl-2-tetrazene (TMT) in benzene solution at [126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141][142] o C were of the order 10 -5 -10 -4 s -1 with an approximate energy of activation of 45 kcal/mol -rather high compared with the gas-phase values given above. Importantly, however, at concentrations of TMT greater than 0.2 M, induced decomposition of the tetrazene becomes important [178].…”

“…This is known as the HERON reaction (Heterocyclic Rearrangement On Nitrogen; Scheme 43) and it often takes place already at room temperature. It is driven by anomeric destabilization of the N-O bond [137,139].…”