organic compounds
excess of an NHR1R2 amine as two moles of amine per mole of
P—Cl bond; Pourayoubi, Karimi Ahmadabad et al., 2011) in a
suitable solvent to yield ClP(O)(OR)(NR1R2) compounds. For
such a reaction, a suitable solvent usually has low solubility of
the C5H5NHCl (or [R1R2NH2]Cl alkyl/aryl ammonium chlo-
ride) by-product, while the solubility of ClP(O)(OR)(NR1R2)
is good in this solvent. In such a case, the by-product is simply
removed by filtration.
The well-known purification method in the preparation of
(R1R2N)2P(O)(OR) amidophosphinates is the dissolution of
the above-mentioned by-product(s) in H2O (Sabbaghi et al.,
2010). This strategy is not suitable for the purification of a
ClP(O)(OR)(NR1R2) compound, as the P—Cl bond is sensi-
tive to moisture.
After purification, ClP(O)(OR)(NR1R2) reacts with an
NHR3R4 amine (1:2 molar ratio) to yield the racemic
(R3R4N)P(O)(OR)(NR1R2) mixed-amide phosphinate; the by-
product of this step, [R3R4NH2]Cl, is removed by dissolving in
H2O.
Figure 1
Displacement ellipsoid plot (50% probability level) and atom-numbering
scheme for (I).
As examples where this or similar procedures have been
used, we can mention [(CH3)2N](p-CH3-C6H4O)P(O)X,
where X = NHC(CH3)3, p-CH3-C6H4NH (Ghadimi et al.,
2009) and NHCH(CH3)2 (Pourayoubi et al., 2007). Another
example is the compound [(ClC2H4)2N](C6H5O)P(O)-
[NHC6H5], which was studied by X-ray crystallography (Orji
et al., 1994). When using [(CH3)2N](p-CH3-C6H4-O)P(O)Cl as
a starting material, some other compounds were also obtained,
for example, with the (N)P(O)(O)(C) skeleton, such as
[(CH3)2N](p-CH3-C6H4O)P(O)CN (Ghadimi et al., 2007),
which was also characterized by X-ray crystallography.
As has been noted in the literature (Pourayoubi, Karimi
Ahmadabad et al., 2011; Pourayoubi, Rheingold et al., 2011;
Sabbaghi et al., 2011), the p-toluidine hydrochloride salt is
relatively insoluble in CH3CN and also in CHCl3 (although the
degree of solubility can be affected by the other starting
materials used in the preparation method). The reaction of
C6H5OP(O)Cl2 and p-CH3-C6H4NH2 (1:2 molar ratio) was
performed in CH3CN (at ice-bath temperature), the [p-CH3-
C6H4NH3]Cl by-product was simply filtered off and the
racemic product ClP(O)(OC6H5)(NHC6H4-p-CH3) was ob-
tained from the solution.
Figure 2
Displacement ellipsoid plot (50% probability level) and atom-numbering
scheme for (II). There is disorder of the C8 methyl group and only the
major part is shown, for clarity.
Up to now, this racemic starting compound has been used
for the preparation of rac-LP(O)(OC6H5)(NHC6H4-p-CH3)
[L = NHC6H11 (Sabbaghi et al., 2011), NHC(CH3)3 (Pour-
ayoubi, Rheingold et al., 2011) and NHCH2C6H5 (Pourayoubi,
Karimi Ahmadabad et al., 2011)]. Here, we used the above-
mentioned starting racemic compound to study the syntheses
and crystal structures of rac-phenyl (N-methylcyclohexyl-
amido)(p-tolylamido)phosphinate, (I) (Fig. 1), and rac-phenyl
(allylamido)(p-tolylamido)phosphinate, (II) (Fig. 2).
Moreover, as the cyclohexylamine (cyclo-C6H11NH2)
hydrochloride salt is also relatively insoluble in CH3CN (and
in CHCl3), we used cyclohexylamine to obtain the starting
phosphorus–chlorine compound ClP(O)(OC6H5)(NH-cyclo-
C6H11) for the first time. This starting compound was used for
the synthesis of rac-phenyl (benzylamido)(cyclohexylamido)-
phosphinate, (III) (Fig. 3). All three compounds crystallize in
centrosymmetric space groups and the racemic character is
reflected by the symmetry.
2. Experimental
2.1. Synthesis and crystallization
All of the syntheses described in this section begin with the
reagents being combined at ice-bath temperature and the
mixture then allowed to come to room temperature for the
rest of the procedure. For the synthesis of (Cl)P(O)-
(OC6H5)(NHC6H4-p-CH3), a solution of 4-CH3–C6H4NH2
(20.0 mmol) in dry chloroform (20 ml) was added to a solution
of (C6H5O)P(O)Cl2 (10.0 mmol) in the same solvent (10 ml) at
273 K. After stirring for 5 h, the solid which formed was
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1182 Pourayoubi et al. C20H27N2O2P, C16H19N2O2P and C19H25N2O2P
Acta Cryst. (2013). C69, 1181–1185