Preparations and transformations of bifunctional exo-2-phosphorus substituted bicyclo[2.2.1]heptanes

Article abstract of DOI:10.1080/10426509608037970

The secondary phosphonate ester exo-2-(dimethoxyphosphoryl)bicyclo[2.2.1]heptane 1 was prepared by literature methods on a mole scale. This synthetic method was extended to include the stereoselective preparation of the exo-diethyl phosphonate analog 3 in 71% yield. Derivatization of these exo-phosphonates 1 and 3 required vigorous conditions, but proceeded in moderate to high yields. The configuration about carbon-2 was retained in all but one case. Isomerization about carbon-2 was observed during the desulfurization of exo-thiophosphonic dichloride 15 with triphenylphosphine at 240°C. A 3:2 ratio of exo-to endo-phosphonous dichlorides 16 resulted. When the reaction was conducted at 100°C, exo-phosphonous dichloride 16 was formed without epimerization at carbon-2 (97% exo isomer). The exo-dichloride 16 isomerized to the endo-isomer upon treatment with triphenylphosphine at 240-260°C. The intermediate phosphaalkene 17 was implicated to precede this isomerization. Moreover, intentional isomerization of the parent compound 3 could be readily effected by treatment with LDA at -78°C. Attempts were also made to stereoselectively displace a benzyl group from the prochiral phosphorus center in exo-dibenzylphosphonium salt 21. However, alkaline hydrolysis of exo-methyldibenzylphosphonium bromide 21 under a variety of conditions gave a 1:1 mixture of exo-2-(benzylmethylphosphoryl)bicyclo[2.2.1]heptane 22.

Full text of DOI:10.1080/10426509608037970

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Phosphorus, Sulfur, and Silicon and
the Related Elements
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PREPARATIONS AND
TRANSFORMATIONS OF BIFUNCTIONAL
EXO-2-PHOSPHORUS SUBSTITUTED
BICYCLO[2.2.1]HEPTANES
Andrew C. Peterson a , Steven M. Levsen a & Sheldon E. Cremer a
a Department of Chemistry , Marquette University , Milwaukee,
Wisconsin, 53201-1881, USA
Published online: 24 Sep 2006.
To cite this article: Andrew C. Peterson , Steven M. Levsen & Sheldon E. Cremer (1996)
PREPARATIONS AND TRANSFORMATIONS OF BIFUNCTIONAL EXO-2-PHOSPHORUS SUBSTITUTED
BICYCLO[2.2.1]HEPTANES, Phosphorus, Sulfur, and Silicon and the Related Elements, 115:1,
241-254, DOI: 10.1080/10426509608037970
To link to this article: http://dx.doi.org/10.1080/10426509608037970
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