Reaction of Nitrile Oxides with Vinylphosphonate 255
TABLE 1 Physical Data of Compounds 3a–i
Anal. Found (Calcd)
Ar
mp (◦C)
Yielda (%)
C
H
N
3a
3b
3c
3d
3e
3f
3g
3h
3i
Ph
p-FC6H4
p-ClC6H4
OCH2OC6H3
m-ClC6H4
2,4-Cl2C6H3
p-CH3C6H4
p-NO2C6H4
o-ClC6H4
Oil
Oil
72–74
Oil
Oil
Oil
Oil
120–121
Oil
67.00
78.54
81.89
72.31
70.80
63.80
76.24
76.21
75.10
54.90 (55.12)
51.75 (51.83)
48.99 (49.15)
51.19 (51.38)
49.01 (49.15)
44.26 (44.34)
56.52 (56.56)
47.46 (47.56)
48.92 (49.15)
6.37 (6.40)
5.74 (5.69)
5.20 (5.39)
5.57 (5.54)
5.41 (5.39)
4.41(4.58)
6.89 (6.78)
5.25 (5.22)
5.35 (5.39)
4.94 (4.95)
4.78 (4.65)
4.28 (4.41)
4.30 (4.28)
4.51 (4.41)
3.81 (3.97)
4.71 (4.71)
8.60 (8.53)
4.22 (4.41)
aIsolated yield based on vinylphosphonate.
have the most favorable orientation because the 1,3-
dipolar cycloaddition reaction is controlled by the
interaction between the LUMO of the dipole and the
HOMO of the dipolarophile. The dipole LUMO has
its largest coefficient on carbon, and this becomes
united with the unsubstituted dipolarophile carbon,
the site of highest HOMO coefficient for a variety of
substituents [4c,4d].
The nitrile N-oxides were prepared from the hy-
droxamic chlorides obtained by the route given in
Scheme 1. The oximes 1 were prepared by known
methods [5]. The hydroxamic chlorides 2 were pre-
pared by passing chlorine gas through the solution
of the oxime in 8 N hydrochloric acid or in or-
ganic solvents at 0◦C for 20 min [6,7]. In case of
piperonal oxime (1d), t-butyl hypochlorite instead
of chlorine gas was used as chlorinating agent (see
Experimental). Originally, compounds 3 were ob-
tained in low yield, that is because nitrile oxides can
dimerize to diarylfuroxan. We found that the dimer-
ization reaction could be reduced in dilute solution
of nitrile oxides. In order to improve the yield, we
made an improvement as follows: Triethylamine is
slowly added to the dilute solution of the hydroxamic
chlorides in that the nitrile oxide as soon as formed
reacted with vinylphosphonate. By this method,
compounds 3 could be obtained in good yield.
The structure of compound 3c was confirmed
by X-ray crystallography. The molecular structure
is shown in Fig. 1. Crystallographic data for 3c:
C26H34Cl2N2O8P2, M = 635.39. Cell parameters from
r
a least-squares fit of the setting angles of 25 re-
flections with θ range 1.84◦ to 25.02◦ at T =
˚
¯
293(2) K, Triclinic, space group P1, a = 11.198(4) A,
TABLE 2 1H NMR Data of Compounds 3a–i: δ (ppm), J (Hz)
3aa
3b
3c
3d
3e
3f
7.46–7.49 (m, 2H), 7.21–7.23 (m, 3H), 4.69 (dd, 1H, 3 JHH = 10.54, 2 JPH = 11.46), 4.02–4.09 (m, 4H), 3.48
(dd, 2H, 3 JHH = 10.60, 3 JPH = 23.29), 1.11–1.21 (m, 6H)
7.54–7.61 (m, 2H), 7.03 (d, 2H, J = 8.42), 4.80 (dd, 1H, 2 JPH = 11.46, 3 JHH = 10.42), 4.12–4.19 (m, 4H), 3.57
(dd, 2H, 3 JHH = 10.43, 3 JPH = 23.16), 1.21–1.31 (m, 6H)
7.58 (d, 2H, J = 8.42), 7.37 (d, 2H, J = 8.41), 4.85 (dd, 1H, 3 JHH = 11.36, 2 JPH = 10.44), 4.14–4.25 (m, 4H),
3.58 (dd, 2H, 3 JHH = 11.36, 3 JPH = 23.02), 1.28–1.37 (m, 6H)
7.23 (s, 1H), 6.97 (d, 1H, J = 8.43), 6.77 (d, 1H, J = 8.43), 5.97 (s, 2H), 4.81 (dd, 1H, 3 JHH = 10.72,
2 JPH = 11.88), 4.16–4.23 (m, 4H), 3.57 (dd, 2H, 3 JHH = 10.74, 3 JPH = 23.05), 1.25–1.36 (m, 6H)
7.23–7.63 (m, 4H), 4.85 (dd, 1H, 3 JHH = 11.16, 2 JPH = 10.86), 4.18–4.25 (m, 4H), 3.58 (dd, 2H, 3 JHH = 11.16,
3 JPH = 23.11), 1.28–1.37 (m, 6H)
7.52 (d, 1H), 7.41 (s, 1H), 7.26 (d, 1H), 4.85 (dd, 1H, 2 JPH = 11.48, 3 JHH = 10.44), 4.16–4.24 (m, 4H), 3.74
(dd, 2H, 3 JHH = 10.44, 3 JPH = 23.05), 1.28–1.36 (m, 6H)
3g
3h
3i
7.47 (d, 2H, J = 8.15), 7.13 (d, 2H, J = 8.15), 4.78 (dd, 1H, 3 JHH = 11.18, 2 JPH = 10.42), 4.12–4.19 (m, 4H),
3.57 (dd, 2H, 3 JHH = 11.08, 3 JPH = 23.28), 2.30 (s, 3H), 1.21–1.31 (m, 6H)
8.25 (d, 2H, J = 8.6), 7.82 (d, 2H, J = 8.6), 4.95 (dd, 1H, 2 JPH = 11.23, 3 JHH = 10.97), 4.19–4.26 (m, 4H), 3.64
(dd, 2H, 3 JPH = 23.28, 3 JHH = 10.97), 1.29–1.38 (m, 6H)
7.18–7.47 (m, 4H), 4.79 (dd, 1H, 2 JPH = 11.2, 3 JHH = 10.94), 4.07–4.17 (m, 4H), 3.69 (dd, 2H, 3 JHH = 10.94,
3 JPH = 23.5), 1.21–1.29 (m, 6H)
aδ 31P of 3a is 18.71 ppm.