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Papers by Andre Pienaar

Phosphor Sulfur Silicon, 1996

Macromolecular Symposia, Aug 1, 2004

Phosphorus Sulfur and Silicon and the Related Elements, 1999

... ANDRE PIENAAR*, CORNELIS M. ERASMUS, MAURITZ WNTZEL and EUGENE H. COWLEY ... Furthermore, the... more ... ANDRE PIENAAR*, CORNELIS M. ERASMUS, MAURITZ WNTZEL and EUGENE H. COWLEY ... Furthermore, the CH function 01 to phosphorus displays characteristic val-ues of the 2JHp=18-20 Hz and 'Jcp=144-148 Hz couplings. ...

Fragmentation of 2-(Dialkylamino)ethyl Phosphate Derivatives. Mechanism Change as a Function of S... more Fragmentation of 2-(Dialkylamino)ethyl Phosphate Derivatives. Mechanism Change as a Function of Substituents at Phosphorus.

Journal of the Chemical Society, Perkin Transactions 2, 1996

ABSTRACT

Heteroatom Chemistry, 1996

Canadian Journal of Chemistry, 1995

Canadian Journal of Chemistry, 1998

α-Lithiated benzylphosphonate esters, XC 6 H 4 CH(Li)PO 3 Et 2 , add regioselectively to cyclohex... more α-Lithiated benzylphosphonate esters, XC 6 H 4 CH(Li)PO 3 Et 2 , add regioselectively to cyclohex-2-enone at the carbonyl group; higher reaction temperatures lead to the reversal to the starting materials, and not to the 1,4-addition. Relative configuration of the C(1) and C α centers in the 1,2-adducts was determined from the 13 C NMR spectra. For 2methylcyclohex-2-enone the regioselectivity of the addition is decreased. The lithioderivative of diethyl 1naphthylmethylphosphonate, C 10 H 7 CH(Li)PO 3 Et 2 , shows reverse regioselectivity yielding the 1,4-, but not the 1,2addition product. The crystal and molecular structure of that 1,4-adduct has been determined and demonstrates that the conformation about the C(1)-C α bond is close to that existing in solution, deduced from the value of the 1 H NMR 3 J HH vicinal coupling constant of the H(1)-C(1)-C α -H hydrogens. The same conformation was also confirmed as the most stable by molecular modeling.

Phosphor Sulfur Silicon, 1996

Macromolecular Symposia, Aug 1, 2004

Phosphorus Sulfur and Silicon and the Related Elements, 1999

... ANDRE PIENAAR*, CORNELIS M. ERASMUS, MAURITZ WNTZEL and EUGENE H. COWLEY ... Furthermore, the... more ... ANDRE PIENAAR*, CORNELIS M. ERASMUS, MAURITZ WNTZEL and EUGENE H. COWLEY ... Furthermore, the CH function 01 to phosphorus displays characteristic val-ues of the 2JHp=18-20 Hz and 'Jcp=144-148 Hz couplings. ...

Fragmentation of 2-(Dialkylamino)ethyl Phosphate Derivatives. Mechanism Change as a Function of S... more Fragmentation of 2-(Dialkylamino)ethyl Phosphate Derivatives. Mechanism Change as a Function of Substituents at Phosphorus.

Journal of the Chemical Society, Perkin Transactions 2, 1996

ABSTRACT

Heteroatom Chemistry, 1996

Canadian Journal of Chemistry, 1995

Canadian Journal of Chemistry, 1998

α-Lithiated benzylphosphonate esters, XC 6 H 4 CH(Li)PO 3 Et 2 , add regioselectively to cyclohex... more α-Lithiated benzylphosphonate esters, XC 6 H 4 CH(Li)PO 3 Et 2 , add regioselectively to cyclohex-2-enone at the carbonyl group; higher reaction temperatures lead to the reversal to the starting materials, and not to the 1,4-addition. Relative configuration of the C(1) and C α centers in the 1,2-adducts was determined from the 13 C NMR spectra. For 2methylcyclohex-2-enone the regioselectivity of the addition is decreased. The lithioderivative of diethyl 1naphthylmethylphosphonate, C 10 H 7 CH(Li)PO 3 Et 2 , shows reverse regioselectivity yielding the 1,4-, but not the 1,2addition product. The crystal and molecular structure of that 1,4-adduct has been determined and demonstrates that the conformation about the C(1)-C α bond is close to that existing in solution, deduced from the value of the 1 H NMR 3 J HH vicinal coupling constant of the H(1)-C(1)-C α -H hydrogens. The same conformation was also confirmed as the most stable by molecular modeling.

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