Diastereotopic groups in two new single-enantiomer structures (R 2)P(O)[NH-(+)CH(C2H5)(C6H5)] (R = OC6H5 and C6H5)

Abstract

The crystal structures of two single-enantiomer compounds, i.e. diphenyl [(R)-(+)-α-ethylbenzylamido]phosphate, C21H22NO3P or (C6H5O)2P(O)[NH-(R)-(+)CH(C2H5)(C6H5)] (I), and N-[(R)-(+)-α-ethylbenzyl]-P,P-diphenylphosphinic amide, C21H22NOP or (C6H5)2P(O)[NH-R-(+)CH(C2H5)(C6H5)] (II), were studied. The different environments at the phosphorus atoms, (O)2P(O)(N) and (C)2P(O)(N), allow the P=O/P—N bond strengths to be compared, as well as the N—H...O=P hydrogen-bond strengths, and P=O/N—H vibrations. The following characteristics related to diastereotopic C6H5O/C6H5 groups in I/II were considered: geometry parameters, contributions to the crystal packing, solution 13C/1H NMR chemical shifts, conformations, and NMR coupling constants. The phosphorus-carbon coupling constants nJ PC (n = 2 and 3) in I and mJ PC (m = 1, 2, 3 and 4) in II were evaluated. For a comparative study, chiral analogous structures were retrieved from the Cambridge Structural Database (CSD) and their geometries and conformations are discussed.