results of microanalysis and molecular weight deter- ... Mol. wt. found. b Kugelrohr distillation. c The integrations were in accordance with the expected structures ...
Reactions of J-Butyl Peresters, XVII The Photochemical Reaction of Dialkyl t-Butylperoxy Phosphates and Alkyl f-Butylperoxy Alkylphosphonates with Cyclohexene and Cyclopentene in the Presence of Copper Ions George Sosnovsky and Gary A. Karas Department of Chemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA Z. Naturforsch. 33b, 1177-1183 (1978); received June 20, 1978 i-Butylperoxy Phosphates, £-Butylperoxy Phosphonates, Copper Ion Catalysis, Triplet Sensitizers, Photochemistry The photochemical reaction of dialkyl f-butylperoxy phosphates (1) and alkyl *-butylperoxy alkylphosphonates (2) with cyclohexene in benzene in the presence RCk (R0) 2 P(0)00C(CH 3 ) 3
^PIOIOOCICH^
1
2
of a catalytic amount of copper(I) bromide produced the corresponding phosphates (3) and phosphonates (4) in 50-70% yield. The analogous reaction of 1 (R0) 2 P(0l0-^> VlOIO-O 01000,CH3)3
. Q
2
. ,0H 3 , 3 C0H U
R = C 2 H 5 . i-C-^.n-C^Hg.R 1 = CHj; R ^ H j , i-C 3 H y , R1 = CjHg yields. In the absence of the copper ions, no phosphate (3) or phosphonates (4) was formed. The thermal reaction is more rapid, i.e., complete within fifteen minutes, as compared to the four to five hours necessary for the photochemical reaction.
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1178
G. Sosnovsky-G. Karas • Photochemistry of l-Butylperoxy Phosphates and Phosphonates
However, the photochemical reaction can be conducted under much milder conditions, i.e., at 5 - 1 0 °C, considerably lower than the elevated temperature of 80 °C which is required for the thermal (i-C3H70)2P(0l00CICH3)3
• f)
CuBr/C6H6 ^ ^OPIOHCK^-i]
1
reaction. The advantage of the reaction at a lower temperature is especially evident during the preparation of the thermally unstable cyclopent-l-en3-yl di-isopropyl phosphate (5). , (CH3)3C0H
5
As it was reported [8], the attempted preparation of 5 via the thermal copper ion catalyzed phosphorylation reaction afforded only 1,3-cyclopentadiene, the decomposition pioduct of phosphate 5, whereas 5 could be isolated and identified when prepared by the milder photochemical reaction. Although 5 could not be purified by distillation under vacuum due to extensive decomposition, the results of microanalysis and molecular weight determination of the undistilled product confirm its identity. The results of the photochemical reaction of dialkyl £-butyl phosphates (1) and alkyl f-butyl peroxy alkylphosphonates (2) with cyclohexene in the presence of copper ions are shown in Tables I and II, respectively.
During the photochemical reaction, it was noted that if benzene was omitted as solvent, the reaction was letarded considerably. Thus, in cyclohexene alone, after four hours, a 3 0 % yield of cyclohex-1en-3-yl di-isopropyl phosphate (3; R = i-C 3 H 7 ) was obtained and 4 3 % of the unreacted perester 1 (R = ;-C 3 H 7 ) was recovered, and only after eight hours could no trace of the perester 1 be detected, and a 5 3 % yield of phosphate 3 (R = i-C 3 H 7 ) was obtained. Thus, it appeared that benzene used here as a solvent was also acting as a photosensitizer. In order to ascertain the role of benzene as a triplet sensitizer [9, 10] in the reaction, the copper ion catalyzed photochemical phosphorylation was conducted in the presence of only a ten mol percent of
Table I. Photochemical preparation of cyclohex-l-en-3-yl dialkyl phosphates (3). (R0L,P(0)00C(CH
Yield b.p. [%] [°C/torr]
R
3'3
69
90-92/0.1
1.4523 234.23 (240)a C12H23O4P
n-C3H7
61
99-101/0.1
1.4537 262.29 a
(260)
C12H23O4P
i-C3H7
53
90-92/0.05
1.4427 262.29 (256)a C14H27O4P
n-C4H9
52
110-115/0. l b 1.4536 290.34 (281)a
a
0OP(O)(OR)2
Microanalysis C10H19O4P
C2H5
^6 6
o
ICH3)3COH
IR [•v, cm -1 ]
Calcd C51.28, H8.18 C = C (1650) Found C 51.07, H8.01 P = 0 (1250-1300) POC (950-1050) Calcd C54.95, H8.84 C = C (1645) Found C54.91, H8.81 P = 0 (1250-1300) POC (950-1050) Calcd C 54.95, H8.84 C = C (1645) Found C 55.29, H 9.18 P = 0 (1250-1300)
m NMR [ , 0 , 0 0 0 ^ 3 , 3
•
O
hCg;T4
' O
0 P
2 R
R1
Yield [%]
CH 3
56
b.p. [°C/torr]
87-89/0.05
i R
*
1CH3'
3COH
U IR [v, cm- 1 ]
m NMR [
^N-OPIOKOC^-i^
1 Cyclohexene [ml]
Benzophenone Inhibitor [mol]
50 50 50
0.0010 0.0010 0.0010
a b
galvinoxyl ROH b DPPH
Inhibitor [mol]
Reaction time [h]
Perester consumed3, [%]
0.0010 0.0010 0.0010
7 11 11
62 75 57
.
( C H 3 l 3 C0H
3 Recovered 1
Yield 3
[%]
b.p. [°C/torr]
ng
31 16 16
38 19 23
88-90/0.05 89-91/0.1 90-92/0.05
1.4436 1.4436 1.4430
[%]
Determined by titration. ROH = 7
1.10 g, 4 3 % recovery) b.p. 63-66 c C/0.05 torr; ri% 1.4143, lit 13 b.p. 64-67 °C/0.1 torr; n\g 1.4148, and cyclohex-l-en-3-yl di-isopropyl phosphate (3, R = i-C 3 H 7 ; 0.80 g, 30%), b.p. 81-83 °C/0.05 torr. Analysis for Ci^H^OiP Calcd C 54.95 H 8.84, Found C 55.13 H 8.76. Photochemical reaction of di-isopropyl t-butylperoxy phosphate (1, R = i-CsH7) with cyclohexene in the presence of copper (I) bromide. An eight hour reaction As described in the general procedure A, a solution of di-isopropyl tf-butylperoxy phosphate (1, R = i-C 3 H 7 ; 2.54 g, 0.010 mol) in cyclohexene (50 ml) in the presence of copper(I) bromide (0.1 g) was irradiated at 5 - 1 0 °C. After 8 h, titration no longer indicated the presence of peroxy phosphate (1) (R = i-CsH?). Following the workup as described in the general procedure A, and distillation using a Kugelrohr apparatus at 83-86 °C/0.2 torr, there was obtained cyclohex-l-en-3-yl di-isopropyl phosphate (3, R = ;-C 3 H 7 ; 1.39 g, 53%), rig 1.4427. Analysis for C12H23O4P Calcd C 54.95 H 8.84 Found C 55.15 H 8.93
molwt: molwt:
262.29, 250.
Photochemical reaction of di-isopropyl t-butylperoxy phosphate (\, R = i-CzH7) with cyclohexene in the presence of copper(I) bromide and a photosensitizer As described in the general procedure A, a solution of di-isopropyl £-butylperoxy phosphate (1,
[1] G. Sosnovsky and D. J. Rawlinson, in E. Müller (ed.): Houben-Weyl, Methoden der Organischen Chemie, Vol. 4/5 a, Georg Thieme Verlag, Stuttgart 1976. [2] G. Sosnovsky, J. Org. Chem. 28, 2934 (1963). [3] G. Sosnovsky, Tetrahedron 21, 871 (1965). [4] G. A. Holder, J. Chem. Soc., Perkin Trans. II 9, 1089 (1972).
R = i-C3H7; 2.54 g, 0.010 mol) in cyclohexene (50 ml) in the presence of copper(I) bromide (0.1 g) and a photosensitizer (0.001 mol, 10 mol percent) was irradiated at 5 - 1 0 °C for 4 - 8 h. After the workup as described in the general procedure A, and distillation using a Kugelrohr apparatus, there was obtained cyclohex-l-en-3-yl di-isopropyl phosphate (3, R = i - C 3 H 7 ) in the yields shown in Table III. Photochemical reaction of di-isopropyl t-butylperoxy phosphate (\, R = i-C^Hi) with cyclohexene in the presence of benzophenone as photosensitizer, copper (I) bromide, and a radical inhibitor As described in the general procedure A, a solution of di-isopropyl f-butylperoxy phosphate (1. R = t-C 3 H 7 ; 2.54 g, 0.010 mol) in cyclohexene (50 ml) in the presence of benzophenone (0.18 g, 0.001 mol, 10 mol percent), copper(I) bromide (0.1 g), and radical inhibitor (0.001 mol, 10 mol percent) was irradiated at 5-10 °C for 7-11 h. After the workup as described in the general procedure A, and distillation using a short path distillation head, there was obtained di-isopropyl J-butylperoxy phosphate (1, R = i-C 3 H 7 ; b.p. 64-68 °C/0.1 torr) and cyclohexl-en-3-yl di-isopropyl phosphate (3, R = i-C3H7) in the yields shown in Table IV. This investigation was supported by a grant from the Graduate School of the University of WisconsinMilwaukee. W e would also like to thank Dr. Maria Konieczny for critically reviewing this manuscript, and Professor E. A. Hill for suggestions concerning the NMR spectra.
[5] V. P. Maslennikov, G. B. Sadikov, and V. P. Sergeeva, Tr. Khim. Khim. Tekhnol. 2, 130 (1973); CA. 81, 44021 j (1974). [6] R. L. Dannley and K. R. Kabre, J. Am. Chem. Soc. 87 (21), 4805 (1965). [7] G. Sosnovsky, G. Karas, and D. J. Rawlinson, Phosphorus 3, 87 (1973).
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1183 G. Sosnovsky-G. Karas • Photochemistry of
