Microwave-assisted synthesis of organophosphorus compounds

Article abstract of DOI:10.1080/10426507.2012.743544

Kabachnik-Fields reactions of a variety of amines, phospha-Michael additions to maleimide derivatives and alcoholysis of dialkyl phosphites were studied under microwave conditions.

Full text of DOI:10.1080/10426507.2012.743544

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Phosphorus, Sulfur, and Silicon and the
Related Elements
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Microwave-Assisted Synthesis of
Organophosphorus Compounds
Erika Bálint a b , Eszter Fazekas a , Judit Takács a , Ádám Tajti a
,
Amadej Juranovič c , Marijan Kočevar c & György Keglevich a
a Department of Organic Chemistry and Technology , Budapest
University of Technology and Economics , Budapest , Hungary
b Research Group of the Hungarian Academy of Sciences at the
Department of Organic Chemistry and Technology, Budapest
University of Technology and Economics , Budapest , Hungary
c Faculty of Chemistry and Chemical Technology, University of
Ljubljana , Ljubljana , Slovenia
Accepted author version posted online: 14 Nov 2012.Published
online: 08 May 2013.
To cite this article: Erika Bálint , Eszter Fazekas , Judit Takács , Ádám Tajti , Amadej Juranovič
, Marijan Kočevar & György Keglevich (2013): Microwave-Assisted Synthesis of Organophosphorus
Compounds, Phosphorus, Sulfur, and Silicon and the Related Elements, 188:1-3, 48-50
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Phosphorus, Sulfur, and Silicon, 188:48–50, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.743544
MICROWAVE-ASSISTED SYNTHESIS OF
ORGANOPHOSPHORUS COMPOUNDS
1
1
1
Erika Ba´lint,1,2 Eszter Fazekas, Judit Taka´cs, Ada´m Tajti,
´
Amadej Juranovicˇ,3 Marijan Kocˇevar,3 and Gyo¨rgy Keglevich1
1Department of Organic Chemistry and Technology, Budapest University of
Technology and Economics, Budapest, Hungary
2Research Group of the Hungarian Academy of Sciences at the Department of
Organic Chemistry and Technology, Budapest University of Technology and
Economics, Budapest, Hungary
3Faculty of Chemistry and Chemical Technology, University of Ljubljana,
Ljubljana, Slovenia
GRAPHICAL ABSTRACT
(R1O)2P(O)H
O
O
O
P
RNH2 + (HCHO)n
+
>P(O)H
R2O
R1O
O
H
+ >P(O)H
P
NR
O
NR
O
RNHCH2P(O)< RN(CH2P(O)<)2
(R2O)2P(O)H
Abstract Kabachnik-Fields reactions of a variety of amines, phospha-Michael additions to
maleimide derivatives and alcoholysis of dialkyl phosphites were studied under microwave
conditions.
Keywords Microwave; Kabachnik-Fields reaction; phospha-Michael addition; alcoholysis
Kabachnik-Fields (phospha-Mannich) reactions, phospha-Michael additions and al-
coholysis take place usually in the presence of catalysts and solvents.1 It was found that
these reactions do not need any solvent and catalyst under microwave (MW) conditions.
The Kabachnik-Fields reaction of pyran-2-one derivatives (1) was carried out with
formaldehyde and >P(O)H species, such as dialkyl phosphites or diphenylphosphine ox-
ide at 120◦C without any solvent and catalyst under MW conditions (Scheme 1). Using
diphenylphosphine oxide as the P-reagent, it was better to carry out the condensation in
acetonitrile.
The three-component condensations of amines, two equivalents of paraformaldehyde
and two equivalents of a >P(O)H species, such as dialkyl phosphites, ethyl phenyl-H-
phosphinate or diphenylphosphine oxide were performed at 100◦C, in most cases, in the
absence of any solvents and catalysts to give the bis(>P(O)) products (3) in yields of
55–98% (Scheme 2).2
Received 16 July 2012; accepted 14 October 2012.
This project was partially supported by the Hungarian Scientific Research Fund (OTKA K83118) and by
the Slovenian-Hungarian Scientific Research program (Project No. BI-HU/11-12-005 and 2011-0637).
Address correspondence to Gyo¨rgy Keglevich, Department of Organic Chemistry and Technology, Budapest
University of Technology and Economics, 1521 Budapest, Hungary. E-mail: ebalint@mail.bme.hu
48

MICROWAVE-ASSISTED SYNTHESES
49
MW
120 °C, 1.5−2 h
Me
O
O
Me
O
O
Y
O
H
O
P
+
(HCHO)n
+
P
Y
Y
R
R
no solvent
NH2
Y
NH CH2
O
O
2
1
R = Me, Ph Y = OMe, OEt, OBu, Ph
74−98%
Scheme 1
O
P
Y1
Y2
MW
100 °C, 1−1.5 h
no solvent
Y1
O
H
CH2
R NH2
2 (HCHO)n
P
+
+ 2
R N
CH2 P Y1
Y2
Y2
O
3
Y1
R = cHex, Bn, 4-MeOPh
OMe OEt
OBn OEt Ph
OBn Ph Ph
OBu
OBu
Y2 OMe OEt
Scheme 2
After double deoxygenation of the bis(diphenylphosphinoylmethyl)amines (3, Y =
Ph), the bisphosphines (4) thus obtained were converted to the platinum complexes (5) in
yields of 45–60% (Scheme 3).
O
P
Ph
P
Ph
Ph
80 °C, 3 days
PhSiH3, N2
25 °C, 1 day
Pt(PhCN)2Cl2, N2
..
Ph
PtCl2
Ph
CH2
PPh2
CH2
CH2
CH2
CH2
R
N
R
N
R N
..
Ar−H
Ar−H
P
Ph
Ph
PPh2
P
CH2
4
Ph
O
5
3, Y = Ph
R = cHex, Bn, 4-MeOPh, Ph, 4-MePh
45−60%
Scheme 3
We have also studied the phospha-Michael addition of >P(O)H species to N-methyl-
and N-phenylmaleimide under MW conditions at 175◦C (Scheme 4).3 The maleic deriva-
tives (6) were obtained in yields of 71–98%, in most cases, without the use of any solvents.
Δ
or MW
175 °C, 2.5−3 h
O
O
O
P
Y1
Y2
Y1
O
H
P
N R
+
N R
O
no solvent
Y2
O
Y1 OMe OEt
Y2 OMe OEt Ph Ph
OEt Ph
6
R = Me, Ph
Scheme 4
It was found that in the alcoholysis of dialkyl phosphites (7), the dialkyl phosphite
with two different alkyl groups (8) was the main product under lower temperature, but

´
E. BALINT ET AL.
50
the fully transesterified product (9) was the exclusive product under higher temperature
(Scheme 5).
MW
100−175 °C
R2O
R1O
O
H
R2O
R2O
O
H
R1O
R1O
O
H
1−2 h
+
R2OH
(25 or 50 eq.)
P
+
P
P
8
9
7
R1 = Me, Et, Bu R2 = Me, Et, iPr, Bu
Scheme 5
REFERENCES
1. Keglevich, G.; Ba´lint, E.; Kiss, N. Zs.; Jablonkai, E.; Gru¨n, A. Curr. Org. Chem. in press.
´
2. Ba´lint, E.; Fazekas, E.; Pinte´r, G.; Szo¨llo˝sy, A.; Holczbauer, T.; Czugler, M.; Drahos, L.;
Ko¨rtve´lyesi, T.; Keglevich, G. Curr. Org. Chem. 2012, 16, 547-554.
3. Ba´lint, E.; Taka´cs, J.; Drahos, L.; Keglevich, G. Heteroatom Chem. 2012, 23, 235-240.