Diazabutadienes in heterocyclic syntheses: Reaction of 1,3-diazabutadienes with 2-oxazolin-5-ones

Article abstract of DOI:10.1016/S0040-4039(00)93452-X

(4+2) Cycloaddition reactions of 1-aryl-4-dimethylamino-2-phenyl-1,3-diazabutadienes with 2-oxazolin-5-ones leading to pyrimidin-6-ones are reported.

Full text of DOI:10.1016/S0040-4039(00)93452-X

"rctrahcdron Letters, Vol.32, No.38, pp 5151-5152, 1991
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DIAZABUTADIENES IN H~TERDCYCLIC SYNTHESES: REACTION OF
I~3-DIAZABUTADIENES WITH 2-OXAZOLIN-S-ONES
Bit Sain, Satyendra P. Singh and 3agir S. Sandhu~
Regional Research Laboratory, 3orhat-785 006, India
Abstract: (4+2) Cycloaddition reactions of 1-aryl-4-dimethylamino-2-phenyl-
1,3-diazabutadienes with 2-oxazolin-5-ones leading to pyrimidin-6-ones are
reported.
Cycloaddition reactions of azadienes have received considerable atten-
tion in heterocyclic synthesis I. In this context 1~2- and 1,4-diazabutadie-
nes have been extensively studied,
in comparison 1,3-diazabutadiones have
not received much attention2. Also, there are conflicting reports in the
case of the reaction of ketanes Lrith 1,3-diazabutadienes 2a.
In continuation to our studios on cycloaddition reactions of azadi-
enes 3, we report that 1-aryl-4-dimethylamino-2-phonyl-1,3-diazabutedienee
(~)2a undergo cycioaddition reactions with 2-exazolin-S-ones (~)4 to yield
novel pyrimidin-6-onea (~) in excellent yields (82-90~). Equimolar quanti-
ties of 4-dimethylamino- 1,2-diphenyl-1,3-diazabutadiene (~)(RI=Ph) and 2-
(4-chlorophenyl)-4-mathyl-2-oxazolin-5-ona
(~)(R2=P-ClC6H4)
when reacted
in dry benzene at room temperature for 12 h, yielded 5- (4-chlorobenzoyl-
amino)-4-dimethylamino-l,2-diphenyl-5-methyl-1,4,St6-tetrahydropyrimidin-
5-one (3a) 5 as white crystalline solid: mp 150- 1S1°C~ yield 90~.
R1
Ph
/R1
Ph
/R l
Ph
N
O
N,~
+
H3H
R 2
W
3
°
N H - ICI - R2
Me2N
NH-C- R2 Me2N
NMe 2
1
II
4
0
Ph
0
2
I
M e 2 N - C H : N-- C - - N - - R .I
o
5_
0
CH3
3.~a: RI=Ph, R2=P-CIC6H4;
3b:
RI=P-MeC6H4, R2=P-CIC6H4, mp 194-195°C;
3._c_c: R l = P h, R2=Ph, mp 171-172°C; 3d: RI=P-MBC6H4, R2=Ph, mp 178-179°C;
3_~B: RI=Ph, R2=CH2Ph, mp 180-181°C; 3f: RI=P-MeC6H4, R2=CH2Ph, mp 198-199°C°
5151

5152
The possible formation of pyrimidinone (4) was eliminated on the basis
of nuclear overhauser enhancement experiments. Further, these experiments
clearly established the formation of one stereoisomer wherein H-4 and methyl
group are cis to each other. The ~ - l a c t a m structure (5) was ruled out on
the basis of 13C NMR and by recording fully deooupled DEPT spectra where no
azomethine CH=N signal was observed in the region S130-170ppm. The reaction
is generalised by varying the subs~ituents in 1,3-diazabutadisne and
2-oxazolin-S-one partners 6.
In conclusion, we have demonstrat~d the inverse electron demand (4÷2)
cyoloaddition of 1,3-diazabutadienes with 2-oxazolin-S-ones affording pyri-
midin-6-ones derivatives. It is worth mentioning that this approach to the
pyrimidine ring involves formation of NI-C 6 and C4-C 5 bonds, which is
rarely reported7.
Acknowledgement: Authors are thankful to RSIC (Lucknow) for 400MHz NMR and
DEPT experiments and Drs. B.J. Wakefield, S.3. Simpson, M.A. Stuckey of
Salford University, UK for NOE experiments and helpful suggestions.
REFERENCES AND NOTES:
Io Reviews and recent references include: e) ~pger, O.L.; Weinreb, S.N.,
Hetero D igls-_Ald@r Methodoloqy in Orqanic Synthesis_,
San Diego, 1987; b) 5andhu, J.S.; Sain, B., H B t e r o ~ , 1987, 26, 777;
c) Boger, D.L.; Kasper, A.M., J. Am. Chem. Sac., 1989, 111, 1517
d) Rivera, M.; Lamy-Schelkens, H.; Sainte, F.; Mbiya, K.; Ghosez, L.,
Tetrahedron Lett., 1988, 29, 4573; e) Lantos, I.; Sheldrake, P.W.;
Academic Press,
;
Wells, A., J. C h e m . . S o _ _ C h e m . Commun., 1989, 1482;
Sakya, S.M., J. Org. Chem., 1988, 53, 1415.
f) Beget, D.L.;
2. a) Luthardt, P.; WUrthwein, F~U., Tetrahedron Lett., 1988, 29, 921
and
references cited therein; b) Barluenga, J.; Tomes, M.; Ballesteros, A.;
Lopez, L.A., Tetrahedron Lett., 1989, 30, 4573.
3. Sain, B.; Baruah, J.N.; Sandhu, J.S., J. Chem. Soc.~ P o r k i n T r a n s I,
1985, 773 and references cited therein.
4. Gotthardt, H.; Huisgen, R.; Bayer, H.O.,J. Am. Chem. See., 1970, 92, 4340.
5. IH NMR data (400MHz)~downfield from Me4Si ; CDC13: 1.72(3H, s, CH3),2.56
(6H, s, N(CH3)2) , 5.42(IH, s, H-a), 6.44(IH, broad e, -NH), 7 . 2 0 - 7 . 4 6
(12H, m, aromatic H), 7.80(2H, m, aromatic
H ortho to CO); 1 3 C N M R (IOOMH~
S; CDC13"17,18(q, CH3), 42.96(q, -N(CH3)2) , 59.88(s, C-5), 7 7 . 4 6 ( d , C - 4 )
127.14-12g.22(aromatic C), 132.50, 134.76, 137.50, 153.2g(s, C-2),
166.05(e, CO), 171.04(s, CO, C-5); I R ( K B r ) ~ m a x (cm-1): 3250, 172@, 1645.
6. All the new compounds gave satisfactory spectroscopic and analytical data.
7. Brown, O.J.: Pyrimidines and their Benzo Derivatives, In Comprehensive
HeterocyolicChemistry: Katritzky, A.R.; Rees, C.W., Eds.;
Press; Oxford, 1984, Vol 3; pp 57-155.
Pergamon
(Received in UK 26 June 1991)