646 Pinchuk et al.
group as compared to the “crown-like” pattern, and
the corresponding resonance will therefore occur at
a weaker field. Besides, such a configuration allows
for three possibilities for the mutual arrangement of
chlorine atoms in the o-chlorophenyl groups lying
on the same side of the plane as the methyl group,
two of the three variants being identical as regards
the disposition of the chlorine atoms relative to the
1
methyl group. Thus, in the H NMR spectrum, the
P CH3 group should resonate in the form of two
signals, with their integral intensities related as 2:1.
This is the case for compound 15c: the methyl group
1
at the phosphorus atom shows the H resonance as
two doublets with the chemical shifts H = 0.35 ppm
(JHP = 14.7 Hz) and H = 0.23 ppm (JHP = 14.7 Hz)
and the integral intensity ratio equal to 2:1.
Steric hindrance caused by aryl groups at po-
sition 4 of the thiophene rings also exert an effect
on the reactivity of phosphines 6b,c. So, unlike the
phosphine 6a, the phosphines 6b,c do not react with
aryl azides, probably, due to increasing steric hin-
drance at the phosphorus atom.
Phosphine 6b, phosphine thioxide 17a, imino-
phospine 18a, and diamidothiophosphonate 26b re-
act with formamide or hydrazine when heated to
give phosphorylated thienopyrimidones 30b, 31b,
32a–34a by means of heterocyclization with partic-
ipation of amidine and ethoxycarbonyl groups. 3-
Aminothienopyrimidone (33a) reacts easily with a
substituted benzaldehyde to give a Shiffs base, as, for
example, 35a (see Scheme 4). Unsymmetrical phos-
phines 9a, 10b, 11b by heating in formamide, do not
react to form thienopyrimidones; this, apparently, is
connected with their lower thermal stability.
SCHEME 2
the shift of the signal of the methyl group is evi-
dently due to the symmetric screening of its pro-
tons by three phenyl groups, which are located in
the “ortho” position to the phosphorus atom. In our
opinion, the phenyl rings and the methyl group at
the phosphorusatom are positioned on the same side
of the conventional plane passing through the phos-
phorus atom perpendicular to the P CH3 bond. This
conjecture is consistent with potential energy val-
ues computed by the molecular mechanics method
(MM+) for the starting trisphosphine molecule 6b
with varied mutual arrangement of the lone elec-
tron pair of the phosphorus atom and the phenyl
rings. As seen from the calculated data, the “crown-
like” configuration of the phenyl rings relative to
the lone electron pair is, on the average, 20–30%
more energetically preferable than other configura-
tions (see Fig. 1). With regard to the fact that the
alkylation of tertiary phosphines is not accompanied
by inversion at the phosphorus atom [5], one can ex-
pect that the “crown-like” configuration will be re-
tained on alkylation. In the molecule of the more
sterically hindered methylposphonium iodide (15c)
(R = 2-ClC6H4), the arrangement of all o-chloro-
phenyl rings on the same side of the plane is ham-
pered. In this case, the calculations suggest that the
most energetically preferable configuration involves
the disposition of the methyl group at the phos-
phorus atom and with only two o-chlorophenyl sub-
stituents on the same side of the plane. This arrange-
ment will result in lesser screening of the methyl
The amidothiophosphonate 26b, phosphine
thioxide 17a, and imino derivative 18a un-
der acidic hydrolysis conditions give derivatives
of 5-(N-formyl)aminothiophenes 36b, 38a, 39a.
The compound 26b, on heating with aqueous-
alcoholic alkali, leads to phosphorylated 5-amino-4-
ethoxycarbonylthiophene (37b), whereas phosphine
6a, phosphine thioxide 17a, and the imino deriva-
tive 18a under the same conditions are hydrolized
with participation of both ethoxycarbonyl and ami-
dine groups, giving phosphorylated derivatives of
5-amino-4-thiophenecarboxylic acid (40a–43a) (see
Scheme 5). The structures of compounds obtained
as shown in Schemes 4 and 5 were determined by
1
31P (Table 1) and H NMR spectroscopy (Tables 4
and 5).
EXPERIMENTAL
All manipulations with moisture-sensitive com-
pounds were performed under an atmosphere of dry