ISSN 0012-5008, Doklady Chemistry, 2019, Vol. 489, Part 1, pp. 257–260. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Doklady Akademii Nauk, 2019, Vol. 489, No. 1.
CHEMISTRY
Mono- and Di(dechloromethylthioylation) of Dichloromethylarenes
with S-Methyl Diethylthiophosphinate
M. B. Gazizova,*, G. D. Valievaa, S. Yu. Ivanovaa, R. A. Khairullina,
Yu. S. Kirillinaa, and Corresponding Member of the RAS I. S. Antipinb
Received August 2, 2019
Abstract—The attack of the thiol sulfur atom (P–SMe) on the methine carbon as the main route of the new
reaction of dichloromethylarenes with S-methyl diethylthiophosphinate has been predicted and experimen-
tally confirmed on the basis of the electronic structure of the S-alkyl esters of P(IV) acids. The processes of
the mono- and di(dechloromethylthioylation) of dichloromethyl group have been realized. A new approach
to the synthesis of the arenecarbaldehyde dimethyl dithioacetals has been developed avoiding the use of gas-
eous highly toxic methyl mercaptan.
DOI: 10.1134/S0012500819110016
The reaction of ambident (P=O, P–O) nucleop- eliminates methyl chloride to give dechlorodiethylth-
hiles, methyl esters of P(IV) acids, with dichlorometh- iophosphinyloxylation product VII. The latter, like its
ylarenes resulting in aromatic aldehydes and acid oxygen analog ArCH(Cl)OP(O)Et2, seems to be
anhydrides has been described in the literature [1, 2].
However, there are no data on the reaction of substi-
tuted benzylidene chlorides with ambident (P=O, P–S)
nucleophiles, in particular, S-methyl diethylthio-
phosphinate.
The aim of this work is to predict and confirm
experimentally the main route of the new reaction of
S-methyl diethylthiophosphinate Ia with dichloro-
methylarenes II and the synthesis of arenecarbalde-
hyde dimethyl dithioacetals without using highly toxic
gaseous methyl mercaptan.
We revealed a new reaction of S-methyl diethylth-
iophosphinate Ia with dichloromethylarenes II. Theo-
retically, we could assume two reaction routes: a and b
(Scheme 1). We suppose two possible variants of
dechloromethylthioylation reaction (route a): without
charge separation via synchronous four-membered
cyclic electron transfer A and through charge separa-
tion via intermediate formation of sulfonium cation B.
The further substitution of chlorine atom in compounds
III by methylthio group should result in dithioacetal V
and diethylphosphinoyl chloride IV (route a).
unstable and decomposes into arenecarbaldehyde
VIII and diethylphosphinothioyl chloride IX.
To select the most probable route from a and b,
we focused our attention on the electron structure of
S-alkyl esters of P(IV) acids R1R2P(O)SR Ia–Ie. Table 1
shows vertical ionization potentials (IP) of the upper
occupied molecular orbitals of S-alkyl esters of P(IV)
acids [3].
The data of Table 1 shows that IP nS for all com-
pounds I are considerably lower (9.03‒9.30 eV) than
IP pπ, 0 (9.81‒10.54 eV), that is, the electron donating
ability of MeS group is considerably higher than that
of the P=O group. Therefore, we draw a conclusion
that route a is the most probable route of this reaction
(Scheme 1). We selected compound Ia for study
because, in contrast to compounds Ic–Ie, it has only
two electron donating centers: SMe and P=O.
Table 1. Vertical ionization potentials of ns, pπ,0, and n0
orbitals of S-alkyl esters of P(IV) acids Iа–Ie
IP ns, eV IP pπ, 0, eV IP n0, eV
No.
Compound
An alternative route is the attack of phosphoryl
oxygen at the methine carbon atom of gem-dichloride II
(route b). Initially formed quasiphosphonium salt VI
Ia MeSP(O)Et2
9.17*
9.03
9.12
9.26
9.30
9.87*
9.81
–
Ib EtSP(O)Et2
–
Ic MeSP(O)(OEt)2
Id EtSP(O)(OEt)2
Ie EtSP(O)(OMe)Me
10.48
10.54
10.12
11.23
10.95
10.70
aKazan State Technological University, Kazan,
420015 Russia
bKazan State University, Kazan, 420008 Russia
* Values obtained from the additivity of IP of n and p
of compounds Ib, Ic, and Id.
orbitals
s
π, 0
*e-mail: mukattisg@mail.ru
257
Gazizov
