Pyrolysis of gemꢀchlorofluorocyclopropanes
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 10, October, 2014
2253
5
×(6—8) mm, the layer height 7.5 cm), the lower and the upꢀ
per parts filled with quartz pieces (reactor C); a quartz tube
350×16 mm) filled in the middle part with cylindrical pieces of
KF(30%)/ꢀAl O (10 g, the layer height 7.0 cm) (reactor D);
J = 47.0 Hz, J = 16.9 Hz). MS, m/z (I (%)): 108, 106 [M]+
1 2 rel
(32, 100), 71 [M – Cl] (62).
+
(
Pyrolysis of gemꢀchlorofluorocyclopropane 1a in reactor B.
1ꢀChloroꢀ1ꢀfluoroꢀ2,2ꢀdimethylcyclopropane 1a (16.20 g,
0.132 mol) was added into a flowꢀtube quartz reactor B filled
with quartz pieces and heated to 450 C at atmospheric pressure
2
3
a quartz tube (350×16 mm) filled in the middle part with
grains of synthetic zeolite NaA (10 g, the layer height 7.5 cm
–
1
(
reactor E).
Pyrolysis of gemꢀchlorofluorocyclopropanes 1a—d in reactor
A. 1ꢀChloroꢀ1ꢀfluoroꢀ2,2ꢀdimethylcyclopropane (1a) (32.40 g,
.264 mol) was added into an empty flowꢀtube quartz reactor A
heated to 450 C at atmospheric pressure in the flow of nitrogen
in the flow of nitrogen (100 mL min ) using a metering pump at
a constant rate of 0.36 g min– over 45 min. The pyrolysis prodꢀ
ucts coming out of the reactor were collected in a trap cooled wit
1
0
a mixture of solid CO —acetone. Then, the pyrolysate was
2
washed with water and 10% aqueous Na CO3 and dried with
2
–
1
(
100 mL min ) using a metering pump at a constant rate of
Na SO . The residue (10.34 g) obtained after removal of the
2
4
–
1
0
.36 g min over 90 min. The pyrolysis products coming out of
drying agent was distilled to isolate 2ꢀfluoroꢀ3ꢀmethylbutaꢀ1,3ꢀ
the reactor were collected in a trap cooled with a mixture of solid
diene (2a) (8.02 g, 74%), b.p. 46—48 C.
CO —acetone. The pyrolysate obtained was washed with water
Pyrolysis of gemꢀchlorofluorocyclopropanes 1a—d in the presꢀ
ence of Al O . A flow of nitrogen was passed through a flowꢀtube
2
and 10% aqueous Na CO and dried with Na SO . The residue
2
3
2
4
2
3
(
20.75 g) obtained after removal of the drying agent was distilled
quartz reactor C filled in the middle part with Al O grains (10 g)
2 3
and heated to 450—550 C at a constant rate of 300 mL min for
–
1
to isolate 2ꢀfluoroꢀ3ꢀmethylbutaꢀ1,3ꢀdiene (2a) 17.10 g (75%)
(
b.p. 46—48 C).
1 h to activate Al O (remove water), then the reactor was cooled
.
2
3
7
1
2
ꢀFluoroꢀ3ꢀmethylbutaꢀ1,3ꢀdiene (2a) . H NMR (CDCl ,
in the flow of N to 230 C. 1ꢀChloroꢀ1ꢀfluoroꢀ2,2ꢀdimethylꢀ
3
2
2
00.1 MHz), : 5.46 (m, 1 H, =CH ); 5.10 (m, 1 H, =CH ); 4.71
cyclopropane (1a) (10.0 g, 81.6 mmol) was added into the reacꢀ
2
2
–
1
(
d, 1 H, —CF=CH—, J = 17.8 Hz); 4.55 (d, 1 H, —CF=CH—,
tor at 230 C in the flow of N (70 mL min ) at a constant rate of
2
19
–1
J = 49.3 Hz); 1.90 (m, 3 H, Me). F NMR (CDCl , 188.3 MHz),
0.10 g min over 100 min. The pyrolysis products coming out of
3
: –109.7 (dd, J = 49.3 Hz, J = 17.8 Hz). MS, m/z (I (%)): 86
the reactor were collected in a trap cooled with a mixture of solid
1
2
rel
+
[
M] (100), 85 (80), 71 (21), 65 (31), 51 (49).
Similarly, pyrolysis of transꢀ1ꢀchloroꢀ1ꢀfluoroꢀ2,3ꢀdimethylꢀ
cyclopropane (1b) (21.60 g, 0.176 mol) at 430 C in reactor A for
CO —acetone. The pyrolysate was washed with water and 10%
2
aqueous Na CO and dried with Na SO . The residue (7.14 g),
2
3
2
4
containing (GLC and NMR data) 94% of 2ꢀchloroꢀ3ꢀmethylꢀ
butaꢀ1,3ꢀdiene (3a) and 3% of 2ꢀfluoroꢀ3ꢀmethylbutaꢀ1,3ꢀdiꢀ
ene (2a), obtained after removal of the drying agent was distilled
at reduced pressure to isolate product 3a (5.67 g, 68%), b.p.
46—48 C (145 Torr).
6
1
0 min gave a pyrolysate (13.85 g), from which 3ꢀfluoropentaꢀ
,3ꢀdienes (2b) (10.18 g, 67%) (Zꢀ2b : Eꢀ2b = 12 : 1) were isolatꢀ
ed by distillation, b.p. 48—52 C.
Similarly, pyrolysis of a mixture of isomeric cisꢀ1ꢀchloroꢀ1ꢀ
fluoroꢀ2,3ꢀdimethylcyclopropanes 1c (syn : anti = 2.2 : 1) (21.60 g,
0
2ꢀChloroꢀ3ꢀmethylbutaꢀ1,3ꢀdiene (2a).16 1H NMR (CDCl3,
200.1 MHz), : 5.60 (m, 1 H, =CH ); 5.45 (m, 1 H, =CH ); 5.42
.176 mol) in reactor A at 460 C for 60 min gave a pyrolysate
2
2
(
(
13.31 g), from which 3ꢀfluoropentaꢀ1,3ꢀdienes 2b (9.73 g, 64%)
(m, 1 H, =CH ); 5.18 (m, 1 H, =CH ); 2.00 (m, 3 H, Me). MS,
m/z (Irel (%)): 104 and 102 [M] (33 and 100), 67 and 65 [M – Cl]
(100 and 50), 41 (64), 39 (62).
2
2
+
Zꢀ2b : Eꢀ2b = 15 : 1) were isolated by distillation, b.p. 48—52 C.
(
Z)ꢀ3ꢀFluoropentaꢀ1,3ꢀdiene (Zꢀ2b). 1H NMR (CDCl3,
2
00.1 MHz), : 6.09 (ddd, 1 H, CH=, J = 27.8 Hz, J = 17.4 Hz,
Similarly pyrolysis of transꢀ1ꢀchloroꢀ1ꢀfluoroꢀ2,3ꢀdimethꢀ
ylcyclopropane (1b) (10.0 g, 81.6 mmol) at 240 C in reactor C
with activated Al O over 100 min gave a pyrolysate (6.88 g)
1
2
J = 11.8 Hz); 5.43 (d, 1 H,=CH , J = 17.4 Hz); 5.09 (d, 1 H,
3
=
2
CH , J = 11.8 Hz); 4.83 (dq, 1 H, CH=CF, J = 37.0 Hz,
2
1
2
3
J = 6.9 Hz); 1.72 (dd, 3 H, Me, J = 6.9 Hz, J = 1.5 Hz).
containing after washing and drying (GLC and NMR data) 93%
of 3ꢀchloropentaꢀ1,3ꢀdienes (3b) (Zꢀ3b : Eꢀ3b = 7 : 1) and 3%
of fluoropentaꢀ1,3ꢀdiene Zꢀ2b, from which the product 3b
(Zꢀ3b : Eꢀ3b = 7 : 1) (5.29 g, 64%) was isolated by distillation at
reduced pressure, b.p. 52—54 C (148 Torr).
2
9
1
2
1
F NMR (CDCl , 188.3 MHz), : –127.1 (dd, 1 F, J = 37.0 Hz,
3
+
J = 27.8 Hz). MS, m/z (Irel (%)): 86 [M] (100), 85 (65), 71 (15),
6
6 (60), 65 (40) (for the mixture of Zꢀ2b and Eꢀ2b).
E)ꢀ3ꢀFluoropentaꢀ1,3ꢀdiene (Eꢀ2b). 1H NMR (CDCl3,
00.1 MHz), : 6.44 (ddd, 1 H, CH=, J = 26.5 Hz, J = 16.5 Hz,
(
2
Similarly, pyrolysis of a mixture of isomeric cisꢀ1ꢀchloroꢀ1ꢀ
fluoroꢀ2,3ꢀdimethylcyclopropanes 1c (synꢀ : antiꢀ = 67 : 33 )
(10.0 g, 81.6 mmol) in reactor C at 240 C over 100 min gave
a pyrolysate (6.82 g) containing after washing and drying (GLC
and NMR data) 91% of 3ꢀchloropentaꢀ1,3ꢀdienes (3b)
(Zꢀ3b : Eꢀ3b = 15 : 1) and 3% of fluoropentaꢀ1,3ꢀdiene Zꢀ2b,
from which product 3b (Zꢀ3b : Eꢀ3b = 15 : 1) (5.07 g) was isolatꢀ
ed by distillation at reduced pressure, b.p. 52—54 C (148 Torr).
1
2
J = 12.0 Hz); 5.55 (d, 1 H, =CH , J = 16.5 Hz); 5.20 (m, 1 H,
3
2
CH=CF); 5.22 (d, 1 H, =CH , J = 12.0 Hz); 1.70 (m, 3 H, Me).
2
19
F NMR (CDCl , 188.3 MHz), : –120.8 (dd, 1 F, J = 26.5 Hz,
J2 = 23.0 Hz). MS, m/z (Irel (%)): 86 [M] (100), 85 (65), 71 (15),
3
1
+
6
6 (60), 65 (40) (for the mixture of Zꢀ2b and Eꢀ2b).
Pyrolysis of a mixture of isomeric 1,2ꢀdichloroꢀ1ꢀfluoroꢀ2ꢀ
methylcyclopropanes 1d (syn : anti = 45 : 55) (16.83 g, 0.118 mol)
was carried out similarly by passing through the reactor A
at 450 C at a constant rate of 0.28 g min–1 for 60 min to obꢀ
tain a pyrolysate (10.39 g), from which 3ꢀchloroꢀ2ꢀfluoroꢀ
butaꢀ1,3ꢀdiene 2d (5.33 g, 42%) was isolated by distillation, b.p.
2
b 1
(Z)ꢀ3ꢀChloropentaꢀ1,3ꢀdiene (Zꢀ3b).
H NMR (CDCl3,
200.1 MHz), : 6.38 (dd, 1 H, J = 16.5, J = 10.5 Hz); 5.84 (q, 1 H,
1
2
J = 6.9 Hz); 5.55 (d, 1 H, J = 16.5 Hz); 5.14 (d, 1 H, J = 10.5 Hz);
1.88 (d, 3 H, Me, J = 6.9 Hz). MS, m/z (I (%)): 104 and 102
rel
+
5
1—52 C.
3
[M] (15 and 46), 67 and 65 [M – Cl] (100 and 50), 41 (40), 39 (53).
ꢀChloroꢀ2ꢀfluorobutaꢀ1,3ꢀdiene (2d). 1H NMR (CDCl3,
(E)ꢀ3ꢀChloropentaꢀ1,3ꢀdiene (Eꢀ3b).
2b
1
H NMR (CDCl3,
2
00.1 MHz), : 5.81 (m, 1 H, =CH ); 5.52 (m, 1 H, =CH ); 5.13
200.1 MHz), : 6.70 (dd, 1 H, J = 16.4 Hz, J = 10.6 Hz); 5.87
2
2
1
2
(
d, 1 H, —CF=CH , J = 47.1 Hz); 4.96 (d, 1 H,—CF=CH ,
(q, 1 H, J = 7.4 Hz); 5.68 (d, 1 H, J = 16.4 Hz); 5.30 (d, 1 H,
J = 10.6 Hz); 1.83 (d, 3 H, Me, J = 7.4 Hz). MS, m/z (Irel (%)):
2
2
19
J = 16.9 Hz). F NMR (CDCl , 188.3 MHz), : –110.1 (dd,
3