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12 H ‐dibenzo[ d,g ][1,3,2]dioxaphosphocins: Synthesis, structures and “through‐space” spin‐spin coupling in their NMR spectra
Author(s) -
Goddard John D.,
Payne Alan W.,
Cook Nick,
Luss Henry R.
Publication year - 1988
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570250241
Subject(s) - chemistry , lone pair , ring (chemistry) , crystallography , alkane stereochemistry , stereochemistry , cyclohexane conformation , nmr spectra database , spectral line , stereospecificity , crystal structure , molecule , hydrogen bond , organic chemistry , physics , astronomy , catalysis
A series of 12 H ‐dibenzo[ d,g ][1,3,2]dioxaphosphocins has been prepared by the reactions of bisphenols with either ethyl phosphorodichloridate or phosphorus pentasulfide. The structures of a pair of cis and trans isomers in this series were elucidated by X‐ray crystallography. Both isomers adopt the boat‐chair conformation in the solid state with the bulky group at C‐12 in the pseudo‐equatorial position. Some flattening of the heterocyclic ring due to the pseudo‐axial ethoxy group was observed in the cis isomer. A novel transannular cyclisation reaction was observed in the mass spectra of the cis isomers and this has allowed us to assign the configurations of all the isomers in the series. The pmr spectra of the compounds have been explained in terms of the rigid boat‐chair conformation; however, as bulky groups were introduced at C‐12, signs of mobility were observed for the cis isomers and an equilibrium was established with mobile boat forms. A stereospecific long‐range coupling between P and the proton at C‐12 could be transmitted “through space” by the antiperiplanar lone‐pair electrons on the ring oxygen atoms.