Synthesis and Structural Peculiarities of Homeomorphic Phosphorus Bridgehead Macrobicyclic Compounds and Novel Dioxaphospha[3.1.1.]p,m,p-cyclophanes

Abstract

The double‐capping reaction of p,m,p‐trinuclear diphenol 4 with PCl3 affords the three homeomorphic isomers 5–7 of a phosphite macrobicyclic compound in low yields. X‐ray structures of out,out‐isomer 5 and in,in‐isomer 6 show very flat macrobicyclic structures with P–P distances of 4.9 Å and 4.5/5.3 Å (two conformers), respectively. The main product of the reaction, however, appears to be diphosphite 8, which contains two dioxaphospha[3.1.1.]p,m,p‐cyclophane subunits. The structural peculiarities of 8 were studied after subsequent oxidation to the corresponding phosphate 12. At room temperature the free rotation either of the para‐phenylene rings and the meta‐phenylene ring in the macrocyclic moieties are hindered as could be demonstrated by means of NOESY measurements. The latter occupies an angled position in respect to the macrocyclic plane. This leads to the existence of conformational isomers due to different relative positions of the meta‐phenylene ring to the P‐OR substituent (cis,trans). We could isolate the cis,cis‐isomer of 12 and establish its structure by X‐ray diffraction.

A Congested in,in-Diphosphine

“…The in,out -isomerism of bridged bicyclic compounds has been extensively studied for compounds containing amines, ammonium ions, and methine groups at bridgehead positions . Much less common are the analogous bridgehead phosphorus compounds, and a recent review of this specific topic provided no examples of an in,in -bisphosphine, , although out,out -bisphosphines (e.g., 1 , Scheme ) and bisphosphonium ions are well-known, and the protonation of medium-ring out,out -bisphosphines can give remarkable out -protonated in,out -isomers (e.g., 2 ). , We recognized that our own studies of in -phosphaphanes had left us with the starting materials for a simple synthesis of the in,in -diphosphine 3 and that this compound would likely possess only high-energy out,out - and in,out -isomers, thus permitting the study of the spectra and reactivity of face-to-face, interacting phosphines. We now report the synthesis and full characterization of compound 3 , its hydrochloride salt, and the corresponding trisulfone, all of which exist as in,in -isomers.…”

Staudinger Reaction at in‐Bridgehead Positions of Phosphorus Macrobicyclic Compounds

“…In the 31 P NMR spectrum the in ‐phosphorus atom in 3 shows a downfield shifted signal at 52.2 ppm. We have previously observed this effect with other P‐bridgehead atoms in macrobicyclic in ‐phosphites and in ‐phosphates 2h–k. The proton and 13 C NMR spectra of compound 3 reflect the D 3 h symmetry of the molecule in solution.…”

“…We previously reported a one‐step procedure to obtain three homeomorphic in , out ‐isomers of phosphite macrobicycles according to a double ‐ capping method 2j,k. The objective of the present paper was to find out whether in , in ‐phosphite 1 or in , out ‐phosphite 6 could be functionalized with large groups at their in ‐positions.…”

“…Whitlock et al5 oxidized in ‐P III atoms in larger phosphorus cryptands. We have already shown the different reactivity of in‐ and out ‐P III atoms of flexible phosphite cage compounds 2h–k…”

Phosphorus-containing macrocyclic compounds: synthesis and properties

“…27,41 According to the 31 P NMR spectroscopic data, the mixture of reaction products contains three homeomorphic P-cryptands 55 ± 57 and compound 58 as the major product (Scheme 18). Apparently, the spatial structure of the bisphenol component allows the intramolecular cyclization of intermediate chlorophosphite giving product 58 to take place as the competitive reaction.…”