7-Azabicyclo[2.2.1]heptane N-Imide as an Intermediate in the Thermal Decomposition of N-Amino-7-Azabicyclo[2.2.1]heptane and the Corresponding Benzenesulphonamide

An intermediate in the thermal decomposition of N-amino-7-azabicyclo[2.2.1]heptane and the corresponding benzenesulphonamide derivative, whose structure is consistent with the formulation 7-azabicyclo[2.2.1]heptane N-imide, affords on thermal fragmentation the hydrocarbon products hexa-1,5-diene, bicyclo[2.2.0]hexane, and cyclohexene and does not rearrange to the corresponding stable 2,3-diazabicyclo[2.2.2]oct-2-ene isomer

A stereochemical test of similarly substituted tetramethylenediazene and cyclic azo decompositions in the gas phase at the same temperature

Valid comparisons of stereochemical tests directed toward an understanding of the behavior of 1,4-diradicals (1) generated by very different methods have been complicated by the lack of examples in the literature where the type of substituents, degree of substitution, and reaction conditions have been the same. We report here the first comparison of the product compositions from similarly substituted tetramethylenediazene1 (2) and six-membered cyclic azo (3) thermal decompositions carried out in the gas phase at the same temperature (306° and 439°). This stereochemical test bears on the important question of whether one can generate the same reactive species (e.g., 1,4-diradicals) by the extrusion of nitrogen 'by two very different methods and hence from two different points on an energy surface

Stereochemical tests of cyclic 1,1-dialkyldiazene fragmentation reactions. Thermal decomposition of N-(cis-(and trans-)2,3-(and 2,5-)dimethylpyrrolidine)nitrenes

The thermal decompositions of presumed 1,1-diazenes, N-(cis-(and trans-)2,5-dimethylpyrrolidine)nitrenes (30), generated from the base-induced decomposition of N-benzenesulfonamido-cis-(and trans-)2,5-dimethylpyrrolidines (28) in octane (and diglyme) at 120°C, afford propene, 1,2-dimethylcyclobutanes, and 1-hexene. The retention/inversion (r/i) ratios of closure products are higher than those found from the corresponding 1,2-diazenes in the gas phase at 306 and 439°C. The thermal decompositions of presumed 1, 1-diazenes, N-(cis-(and trans-)2,3-dimethylpyrrolidine)nitrenes (31 ), generated from the base-induced decomposition of N-bcnzenesulfonamido-cis-(and trans-)2,3-dimethylpyrrolidine (29) in octane (and diglyme) at ≤ 120°C, afford 2-butenes and 1,2-dimethylcyclobutanes. The stereospecificity in the 2-butanes and 1,2-dimethylcyclobutanes is high. Analysis of the data indicates a 51% direct cleavage pathway to trans-2-butene and ethylene and 49% 1,4-biradical pathway from the decomposition of N-(trans-(2,3-dimethylpyrrolidine)nitrenc (trans-31 ). Similarly, N-(cis(2,3-dimethylpyrrolidine)nitrene (cis-31) affords a 38% direct cleavage pathway to cis-2-butene and ethylene and 62% 1,4-biradical pathway. Whether this stereospecific cleavage reaction is a concerted cycloreversion or results from a diazenyl biradical precursor cannot be distinguished from the data. The relative rates of rotation, cleavage, and closure for 3-methyl-1,4-pentanediyl (35C and 35T) generated from the corresponding tetramethylene-1, 1-diazenes (31) in octane at ≤ 120°C were determined. From 35C, k(cleavage)/ k(closure) = 1.6, k(closure)/ k(rotation) = 4.9. From 35T, k(cleavage)/ k(closure) = 4.7 and k(closure) / k(rotation) = 3.1. Thermal decomposition of N-methanesulfonamido-cis-(and trans-)2,3-(and 2,5-)dimethylpyrrolidines (39 and 38, respectively) in the gas phase at 306 and 439°C affords hydrocarbon products consistent with the intermediacy and subsequent decomposition of I, 1-diazenes (30 and 31). The retention/inversion ratios in the closure products suggest that 1,4 biradicals generated from cyclic 1,1-dialkyldiazene decompositions in the gas phase at 306 and 439°C behave much like those from cyclic 1,2-diazene decompositions under similar conditions. 1,4 biradicals with secondary radical centers generated from the same 1,1-dia,zenes behave more stereospecifically in solution at lower temperatures (120°C)

A stereochemical test of similarly substituted tetramethylenediazene and cyclic azo decompositions in the gas phase at the same temperature

Valid comparisons of stereochemical tests directed toward an understanding of the behavior of 1,4-diradicals (1) generated by very different methods have been complicated by the lack of examples in the literature where the type of substituents, degree of substitution, and reaction conditions have been the same. We report here the first comparison of the product compositions from similarly substituted tetramethylenediazene1 (2) and six-membered cyclic azo (3) thermal decompositions carried out in the gas phase at the same temperature (306° and 439°). This stereochemical test bears on the important question of whether one can generate the same reactive species (e.g., 1,4-diradicals) by the extrusion of nitrogen 'by two very different methods and hence from two different points on an energy surface

Stereochemical tests of cyclic 1,1-dialkyldiazene fragmentation reactions. Thermal decomposition of N-(cis-(and trans-)2,3-(and 2,5-)dimethylpyrrolidine)nitrenes

The thermal decompositions of presumed 1,1-diazenes, N-(cis-(and trans-)2,5-dimethylpyrrolidine)nitrenes (30), generated from the base-induced decomposition of N-benzenesulfonamido-cis-(and trans-)2,5-dimethylpyrrolidines (28) in octane (and diglyme) at 120°C, afford propene, 1,2-dimethylcyclobutanes, and 1-hexene. The retention/inversion (r/i) ratios of closure products are higher than those found from the corresponding 1,2-diazenes in the gas phase at 306 and 439°C. The thermal decompositions of presumed 1, 1-diazenes, N-(cis-(and trans-)2,3-dimethylpyrrolidine)nitrenes (31 ), generated from the base-induced decomposition of N-bcnzenesulfonamido-cis-(and trans-)2,3-dimethylpyrrolidine (29) in octane (and diglyme) at ≤ 120°C, afford 2-butenes and 1,2-dimethylcyclobutanes. The stereospecificity in the 2-butanes and 1,2-dimethylcyclobutanes is high. Analysis of the data indicates a 51% direct cleavage pathway to trans-2-butene and ethylene and 49% 1,4-biradical pathway from the decomposition of N-(trans-(2,3-dimethylpyrrolidine)nitrenc (trans-31 ). Similarly, N-(cis(2,3-dimethylpyrrolidine)nitrene (cis-31) affords a 38% direct cleavage pathway to cis-2-butene and ethylene and 62% 1,4-biradical pathway. Whether this stereospecific cleavage reaction is a concerted cycloreversion or results from a diazenyl biradical precursor cannot be distinguished from the data. The relative rates of rotation, cleavage, and closure for 3-methyl-1,4-pentanediyl (35C and 35T) generated from the corresponding tetramethylene-1, 1-diazenes (31) in octane at ≤ 120°C were determined. From 35C, k(cleavage)/ k(closure) = 1.6, k(closure)/ k(rotation) = 4.9. From 35T, k(cleavage)/ k(closure) = 4.7 and k(closure) / k(rotation) = 3.1. Thermal decomposition of N-methanesulfonamido-cis-(and trans-)2,3-(and 2,5-)dimethylpyrrolidines (39 and 38, respectively) in the gas phase at 306 and 439°C affords hydrocarbon products consistent with the intermediacy and subsequent decomposition of I, 1-diazenes (30 and 31). The retention/inversion ratios in the closure products suggest that 1,4 biradicals generated from cyclic 1,1-dialkyldiazene decompositions in the gas phase at 306 and 439°C behave much like those from cyclic 1,2-diazene decompositions under similar conditions. 1,4 biradicals with secondary radical centers generated from the same 1,1-dia,zenes behave more stereospecifically in solution at lower temperatures (120°C)

Thermal decomposition of cis- and trans-3,4- and -3,6-dimethyl-3,4,5,6-tetrahydropyridazines. Evidence against the hot diradical postulate for azo decompositions

Tetramethylene diradicals are the hypothetical reactive intermediates postulated to intervene in the dimerization of olefins and the thermal cleavage of cyclobutanes. Experimental efforts using stereochemical probes have been directed toward generating these reactive intermediates from different appropriately substituted precursors (olefins, cyclobutanes, azo compounds, diazenes, ketones, and sulfolanes) in order to characterize their behavior. Unfortunately differences in substitution, temperature, and reaction conditions have made direct comparisons of product distributions difficult

Experimental determination of the relative rates of rotation, cleavage, closure, and 1,5-hydrogen shift for 3-methyl-1,4-pentanediyl. Evidence for 1,4 biradicals as common intermediates from different precursors, 3,4-(and 3,6-)dimethyl-3,4,5,6-tetrahydropyridazines and 1,2-dimethylcyclobutanes

Thermal decomposition of cis- and trans-3,6-dimethyl-3,4,5,6-tetrahydropyridazine (11 and 12, respectively) affords propene, els- and trans-1,2-dimethylcyclobutanes, and 1-hexene. The stereochemistry of the products is consistent with a 1,4-biradical intermediate(s) 2,5-hexanediyl, which has the properties k(rotation) ~ k(cleavage) ~ k(closure). At 439°C the retention/inversion (r/I) ratios for the 1,2-dimethylcyclobutane products are 1.7 and 1.7 from 11 and 12, respectively. At 306°C, these ratios are 1.9 and 2.2, respectively. The results indicate that when the thermal reactions of cyclic azo compounds and cyclobutanes of similar substitution are compared at similar temperatures, the stereospecificities are similar. We conclude that stereoretention is dependent on both substitution and temperature, i.e., stereospecificity increases as substitution at the radical center increases and as the temperature is lowered. The thermal decomposition of cis- and trans-3,4-dimethyl-3,4,5, tetrahydropyridazine (19 and 20, respectively) allows a dissection of direct vs. 1,4-biradical pathways in six-membered cyclic azo decompositions, e.g., 36% direct/64% 1,4 biradical from cis-19 and 32% direct/68% 1,4 biradical from trans-20. The ...tive rates of rotation, cleavage, and closure for azo-generated 1,4 biradicals, 3-methyl-1,4-pentanediyl (ST and SC), w... determined. For 8T, k (cleavage)/ k( closure) = 1.6 and k(closure) / k(rotation) = 1.9. For SC, k (cleavage)/ k( closure) = 1.8 and k( closure)/ k(rotation) = 0. 7. These relative rates of rotation, cleavage, and closure generate similar trans-/cis-2-butene ratios as found in the pyrolyses of cis- and trans-1,2-dimethylcyclobutanes at the same temperature and phase. We conclude they pass the stereochemical test for identity, indicating evidence for common 1,4-biradical intermediates from two different precursors (1,2-diazenes and cyclobutanes). Finally, the data are compared with the recent literature values reported for the dimerization of ethylene and 2-butenes

Experimental determination of the relative rates of rotation, cleavage, closure, and 1,5-hydrogen shift for 3-methyl-1,4-pentanediyl. Evidence for 1,4 biradicals as common intermediates from different precursors, 3,4-(and 3,6-)dimethyl-3,4,5,6-tetrahydropyridazines and 1,2-dimethylcyclobutanes

Thermal decomposition of cis- and trans-3,6-dimethyl-3,4,5,6-tetrahydropyridazine (11 and 12, respectively) affords propene, els- and trans-1,2-dimethylcyclobutanes, and 1-hexene. The stereochemistry of the products is consistent with a 1,4-biradical intermediate(s) 2,5-hexanediyl, which has the properties k(rotation) ~ k(cleavage) ~ k(closure). At 439°C the retention/inversion (r/I) ratios for the 1,2-dimethylcyclobutane products are 1.7 and 1.7 from 11 and 12, respectively. At 306°C, these ratios are 1.9 and 2.2, respectively. The results indicate that when the thermal reactions of cyclic azo compounds and cyclobutanes of similar substitution are compared at similar temperatures, the stereospecificities are similar. We conclude that stereoretention is dependent on both substitution and temperature, i.e., stereospecificity increases as substitution at the radical center increases and as the temperature is lowered. The thermal decomposition of cis- and trans-3,4-dimethyl-3,4,5, tetrahydropyridazine (19 and 20, respectively) allows a dissection of direct vs. 1,4-biradical pathways in six-membered cyclic azo decompositions, e.g., 36% direct/64% 1,4 biradical from cis-19 and 32% direct/68% 1,4 biradical from trans-20. The ...tive rates of rotation, cleavage, and closure for azo-generated 1,4 biradicals, 3-methyl-1,4-pentanediyl (ST and SC), w... determined. For 8T, k (cleavage)/ k( closure) = 1.6 and k(closure) / k(rotation) = 1.9. For SC, k (cleavage)/ k( closure) = 1.8 and k( closure)/ k(rotation) = 0. 7. These relative rates of rotation, cleavage, and closure generate similar trans-/cis-2-butene ratios as found in the pyrolyses of cis- and trans-1,2-dimethylcyclobutanes at the same temperature and phase. We conclude they pass the stereochemical test for identity, indicating evidence for common 1,4-biradical intermediates from two different precursors (1,2-diazenes and cyclobutanes). Finally, the data are compared with the recent literature values reported for the dimerization of ethylene and 2-butenes