Theory of cycloaddition reactions

1,3-Dipolar cycloaddition to the FeSC fragment 20. Preparation and properties of carbonyliron complexes of di-thiooxamide. Reactivity of the mononuclear (di-thiooxamide)Fe(CO)3 towards dimethyl acetylenedicarboxylate

“…From these investigations two important conditions with respect to the 1,3-dipolar reactivity emerged; (i) since the Fe X C (X= NR, O) fragment can be classified as nucleophilic type I 1,3-dipole [22][23][24][25][26][27], a relatively high electron density is required [1,6,8,10,[28][29][30], and (ii) because the cycloaddition proceeds over the Fe X C (X= NR, O) fragment, the metal atom must be able to increase its co-ordination number and oxidation state.…”

Evidence for a [2+4] cycloaddition in the ion‐molecule reaction of ionized 1,3‐butadiene with vinyl ethyl (methyl) ether in the gas phase

“…The evidence for the occurrence of a [2 + 41 cycloaddition reaction in the ionized 1,3-butadiene/VME system may be summarized as follows: (1) The methanol lost in the reaction of [1,1,4,' is exclusively CH,OD. (2) There is a close similarity between the EI spectrum of 4-methoxycyclohexene and the ICR spectrum of the 1,3-butadiene/VME system.…”

“…Helium was admitted to the collision chamber until the analyser pressure was increased to an indicated lop6 Torr. 1,vinyl ethyl ether,1,isoprene,1,1,3,hexatriene were commercial samples from standard sources. 1,3-Butadiene-d6 was obtained from Merck Sharp and Dohme.…”

4-(4-Chloro-phenyl)-pyrimidinium ylides. 1. Structure, stability, reactivity

“…We used the General Theory of Perturbation Limited to the Frontier Molecular Orbitals. [34][35][36][37][38] The geometry of the 4-(4-chlorophenyl)pyrimidinium benzoyl methylide 5a (for the energetically most favoured geometry, the heat of formation is ∆H= 63.174 kcal/mol), the atomic charges, the coefficients of the atomic orbitals, and the values of the energies of the frontier molecular orbitals ( An analysis of the data from Table 2 leads to the following conclusions: -the ylide carbanion center, C-7, has a negative atomic charge, less than unity, but significant; -the ylide nitrogen atom, N-1, has a positive atomic charge, less than unity, significant but smaller (in absolute value) than the ylide carbanion; -the α-endocyclic carbon atoms, C-2 and C-6, have small negative atomic charges, both being less than unity. Table 2.…”