Phosphorus Compounds With Eight-Membered Heterocyclic Systems: Synthesis and Three-Dimensional Structure

Abstract

An analysis of the conformational behaviors of phosphorus compounds with different types of eightmembered heterocyclic systems (saturated and unsaturated organic and inorganic systems, their metal complexes as well as metallocycle derivatives) is given. By using the quantitative criteria (torsional angles and puckering parameters) as a description of the conformational state, it is possible to provide a sufficiently complete and consistent picture of their three-dimensional structure in the solid and solution state. A conclusion about the electronic effects which govern their conformational behavior is made. Special attention is paid to the description of synthetic routes to eight-membered heterocycles and of spectroscopic indicators for the reliable identification of conformers.

Synthesis and Conformation of Chiral Eight-Membered 12H-Dibenzo[d,g][1,3,2]dioxaphosphocins1

“…The downfield signal is further split by five-bond J coupling to phosphorus ( 5 J HP = 2.2 Hz). The magnitude of the observed geminal coupling constant and the observation of five-bond coupling of the downfield proton signal to phosphorus are consistent with a boat−chair conformation in solution, vide ante (Figure ). ,− …”

“…Studies on the conformation of the 12 H -dibenzo[ d,g ][1,3,2]dioxaphosphocin ring have appeared only within the past 10 years. Quite recently, several reviews have appeared on the subject. ,− The commonly accepted nomenclature to describe the conformation of eight-membered rings is used herein; namely the boat−chair ( C s symmetry), boat−boat ( C s symmetry), twist-boat ( C 1 symmetry), and twist ( C 2 symmetry), which are abbreviated BC, BB, TB, and T, respectively. − Arshinova has noted that the boat conformer ( C 1 symmetry; abbreviated B) should also be considered as it is commonly found in the solid state. − The B conformation represents a highly distorted TB geometry about halfway between the symmetric C 2 T and BB geometries . The B conformation is characterized by a C aromatic −O−P−O torsion angle of 0° …”

“…The originally observed dependence of the magnitude of the couplings of the C(12) geminal protons in substituted 5,6,7,12-tetrahydrodibenzo[ a,d ]cyclooctenes upon ring conformation − was extended to probe the conformation of 12 H -dibenzo[ d,g ][1,3,2]dioxaphosphocins in solution. − The observation of a geminal coupling constant of −12 to −13 Hz with observable 5 J HP coupling of 2−4 Hz in 12 H -dibenzo[ d,g ][1,3,2]dioxaphosphocins is consistent with a BC conformation with the exocyclic substituent on phosphorus assuming a pseudoequatorial placement . Both the magnitude of the observed coupling constants and the observation of 5 J HP suggest that 7 and 8 assume a biased BC conformation in solution with a pseudoequatorial substituent on phosphorus.…”

Conformations of 1,3,6,2-dioxaselenaphosphocanes

“…We have recently synthesized 2-substituted 1,3,6,2-dioxaselenaphosphocane 2-oxides, sulfides and selenides 1,2 and been interested in the elucidation of their conformation in comparison with the reported conformations of similar 8-membered 1,3,6,2-trioxaphosphocanes, 1,3,6,2-dioxasulfaphosphocanes and 1,3,6,2-dioxaazaphosphocanes. 3 A chair-chair conformation was suggested for 2-methyl-1,3,6,2-trioxaphosphocane 1 and its 2-sulfide 2 in solution 4 and a crown conformation with the sulfur atom axial and the methyl group equatorial on the phosphorus atom was found for the molecule 2 in the crystal state. 5 An equilibrium between two twisted chair-chair conformations 3a and 3b was proposed for 2-methyl-1,3,6,2dioxasulfaphosphocane 2-oxide 3 and an equilibrium between two chair-chair conformations 4a and 4b for 2,6-dimethyl-1,3,6,2-dioxaazaphosphocane 4 in solution (Chart 1 and Scheme 1).…”

Phosphorylation of the 2,2'-Dihydroxy-1,1'-dinaphthylmethane and Synthesis of Phosphamacrocycles on its Basis

“…[8,9] Phosphorylation of 1 with triamidophosphites and other acyclic derivatives have resulted in formation of cyclic products -1,3,2-dioxaphophacines. [10][11][12] At the same time, compound 1 has never been applied as a building block in synthesis of macrocyclic systems.…”