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Hydroiminoformylation of olefins with isocyanides and hydrogen in the presence of ruthenium complex catalysts
Journal of Molecular Catalysis, 60 (1990)
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L5 - L7
Hydroiminoformylation of Olefins with Isocyauides and Hydrogen in the Presence of Ruthenium Complex Catalysts MASATO TANAKA* and TERUYUKI
HAYASHI
National Chemical Laboratory
for Industry, Tsukuba, Zbaraki 305 (Japan)
(Received December 15,1989;
accepted February 5,199O)
Summary Hydroiminoformylation of olefins with cyclohexylisocyanide and hydrogen was found to proceed in the presence of low-valent ruthenium complex catalysts to give aldimines. Carbon monoxide is a versatile building block for organic synthesis in the current chemical industry. In particular, hydroformylation of olefins with carbon monoxide and hydrogen is one of the most important applications [l]. As is widely recognized, isocyanides are isoelectronic to carbon monoxide. Hence they form similar coordination compounds and often exhibit similar reactivities [2]. However, the reaction of olefins with isocyanides and hydrogen leading to the formation of aldimines, namely hydroiminoformylation, seems to have never been explored. We now report the first examples of hydroiminoformylation of olefins taking place in the presence of ruthenium carbonyl complexes. A benzene (5 ml) solution of styrene (10 mmol), cyclohexylisocyanide (2.5 mmol) and Ru~(CO),~ (0.017 mmol) was treated with hydrogen (50 atm at room temperature) at 150 “C for 12 h. GLC analysis of the resulting mixture showed the formation of N-(2-phenylpropylidene)cyclohexylamine (la) in 30.4% based on the charged amount of the isocyanide (eqn. (1)). Ethylbenzene was formed in only 2.8% (based on styrene), though
Q 0
CH-CH,
+
u
NC + H, -
CRUI
40
*Author to whom correspondence 0304-5102/90/$3.50
CH,
CH’
(1)
H1. \ la should be addressed. 0 Elsevier Sequoia/Printed
in The Netherlands
L6
Rus(C0)i2 has been known to catalyze undesired hydrogenation of olefins under the hydroformylation conditions [3]. Kugelrohr distillation of the reaction mixture (80 - 90 “C/O.2 torr) afforded 83 mg of analytically pure sample, the structure of which was fully supported by spectroscopy*. Pent-1-ene also reacted similarly under the identical conditions to give N-(2-methylpentylidene)cyclohexylamine (lb, 3.0%), N-hexylidenecyclohexylamine (Zb, 13.6%), N-(2-methylpentyl)cyclohexylamine (3b, O.l%), and N-hexylcyclohexylamine (4b, 2.8%) as shown in eqn. (2)**.
+
Y 3b
NH
+
-NH 4b
In contrast with the styrene reaction, hydrogenation of 1-pentene extensively proceeded. In addition, N-methylcyclohexylamine was also formed in 16% yield (based on the &cyanide charged) presumably through hydrogenation of the isocyanide. There are several papers reporting homogeneous hydrogenation of isocyanide [4]. However, pentene reactions by the present procedure were usually more or less accompanied by precipitation of insoluble species. At the moment, we cannot unequivocally decide whether the hydrogenation of the isocyanide was homogeneously or heterogeneously catalyzed. It is interesting to note that the present reaction bears a seeming resemblance in regioselectivity to hydroformylation. Thus, the selective *The aldimine la: IR (neat) 1665 cm-r (C=N); ‘H NMR (CDC13, TMS); 6 1.0 - 1.9 (m, 10 H, (CHz)s), 1.41 (d, J= 7 Hz, 3H, CHs), 2.75 - 3.10 (m, lH, N-CH), 3.60 (dq, lH, CeHsCfI), 7.17 - 7.36 (m, 5H, CeHs), 7.67 ppm (d, J= 6 Hz, lH, CH=N); MS m/e (relative intensity) 215 (8, M+), 172 (6), 132 (5), 110 (42), 105 (23), 83 (100). **The aldimine lb: IR (neat) 1662 cm-’ (C=N); ‘H NMR (CDC13, TMS); 6 0.88 (t, J= 7 Hz, 3H, CXsCH2), 1.00 (3H, d, 5=7 Hz, CFIsCH), 1.10-1.85 (m, 14H, CHsCFIzCI& and CH2 groups in the cyclohexane ring), 2.05 - 2.45 (m, lH, CHCH=N), 2.65 - 3.05 (m, lH, CHN=), 7.42 ppm (d, J = 6 Hz, lH, CH=N); MS m/e (relative intensity) 181 (1.6, M+), 180 (l), 152 (17), 139 (92), 110 (37), 96 (58), 83 (58), 58 (85), 55 (loo), 41 (97). The aldimine 2b: IR (neat) 1666 cm-l (C=N); ‘H NMR (CDC13, TMS); 6 0.9 (t, J= 7 HZ, 3H, CHs), 1.0 - 2.0 (m, 16H, CH3CEI2CH2CfI2 and CH2 groups in the cyclobexane ring), 1.25 (m, 2H, CHzC=N), 2.90 (m, lH, CHN=), 7.68 ppm (t, J= 5 Hz, lH, CH=N); MS m/e (relative intensity) 181 (0.2, M+), 180 (0.2), 138 (8), 125 (14). 110 (13), 83 (lo), 82 (21), 56 (16), 55 (34), 44 (100).
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formation of la in the reaction of styrene stems from preferential attack of ruthenium species on the inner olefinic carbon followed by migratory insertion of isocyanide in the resulting alkylruthenium complex. This is very similar to the preferential formation of the branched aldehyde usually encountered in hydroformylation of styrene catalyzed by ruthenium [5] or other catalysts [6]. Likewise, the regioisomeric ratio in the reaction of pentene is also similar to that reported for ruthenium-catalyzed hydroformylation of l-pentene [ 51. In pentene reactions, [(PPh,),N][HRu,(CO),,] (the total yield of lb, Zb, 3b, and 4b = 18.4%) and Ru(CO),(PPh,), (the total yield = 10.4%) could also be used as the catalyst, the latter being slightly less active. Typical hydroformylation catalysts such as Rh4(C0)i2, CO,(CO)~ and HRh(CO)(PPha)s showed very little activity, the total yield being less than 0.1%. and HPt(SnC13)(PPh3), were totally inactive. In Pes(C0) 12y RuCl,(PPh,), any event, the catalyst performance in the present reactions is still low as compared with hydroformylation. This may be associated with isocyanides being stronger u-donors, which hinder the generation of a vacant coordination site required for the occurrence of the reaction. Search for more efficient catalysis is under way. References 1 B. Corn&, in J. FaIbe (ed.), New Syntheses with Carbon Monoxide, Springer-Verlag, Berlin, 1980, p. 1. 2 E. Singleton and H. E. Oosthuizen, Adv. Organometall. Chem., 22 (1983) 209. 3 H. F. Schultz and F. Bellstedt, Znd. Eng. Chem., Prod. Res. Dev., 12 (1973) 176; M. Bianchi, G. Menchi, P. Frediani, U. Matteoli and F. Piacenti, J. Organometall. Chem., 247 (1983) 89. 4 E. Band, W. R. Pretzer, M. G. Thomas and E. L. Muetterties, J. Am. Chem. Sot., 99 (1977) 7380; E. L. Muetterties, E. Band, A. Kokorin, W. R. Pretzer and M. G. Thomas, Znog. Chem., 19 (1980) 1552; S. T. McKenna, R. A. Anderson and E. L. Muetterties, Organometallics, 5 (1986) 2233. 5 T. Hayashi, Z. H. Gu, T. Sakakura and M. Tanaka, J. Organometall. Chem., 352 (1988) 373. 6 T. Hayashi, M. Tanaka and I. Ogata, J. Mol. Catal., 13 (1981) 323 and references cited therein.
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L5 - L7
Hydroiminoformylation of Olefins with Isocyauides and Hydrogen in the Presence of Ruthenium Complex Catalysts MASATO TANAKA* and TERUYUKI
HAYASHI
National Chemical Laboratory
for Industry, Tsukuba, Zbaraki 305 (Japan)
(Received December 15,1989;
accepted February 5,199O)
Summary Hydroiminoformylation of olefins with cyclohexylisocyanide and hydrogen was found to proceed in the presence of low-valent ruthenium complex catalysts to give aldimines. Carbon monoxide is a versatile building block for organic synthesis in the current chemical industry. In particular, hydroformylation of olefins with carbon monoxide and hydrogen is one of the most important applications [l]. As is widely recognized, isocyanides are isoelectronic to carbon monoxide. Hence they form similar coordination compounds and often exhibit similar reactivities [2]. However, the reaction of olefins with isocyanides and hydrogen leading to the formation of aldimines, namely hydroiminoformylation, seems to have never been explored. We now report the first examples of hydroiminoformylation of olefins taking place in the presence of ruthenium carbonyl complexes. A benzene (5 ml) solution of styrene (10 mmol), cyclohexylisocyanide (2.5 mmol) and Ru~(CO),~ (0.017 mmol) was treated with hydrogen (50 atm at room temperature) at 150 “C for 12 h. GLC analysis of the resulting mixture showed the formation of N-(2-phenylpropylidene)cyclohexylamine (la) in 30.4% based on the charged amount of the isocyanide (eqn. (1)). Ethylbenzene was formed in only 2.8% (based on styrene), though
Q 0
CH-CH,
+
u
NC + H, -
CRUI
40
*Author to whom correspondence 0304-5102/90/$3.50
CH,
CH’
(1)
H1. \ la should be addressed. 0 Elsevier Sequoia/Printed
in The Netherlands
L6
Rus(C0)i2 has been known to catalyze undesired hydrogenation of olefins under the hydroformylation conditions [3]. Kugelrohr distillation of the reaction mixture (80 - 90 “C/O.2 torr) afforded 83 mg of analytically pure sample, the structure of which was fully supported by spectroscopy*. Pent-1-ene also reacted similarly under the identical conditions to give N-(2-methylpentylidene)cyclohexylamine (lb, 3.0%), N-hexylidenecyclohexylamine (Zb, 13.6%), N-(2-methylpentyl)cyclohexylamine (3b, O.l%), and N-hexylcyclohexylamine (4b, 2.8%) as shown in eqn. (2)**.
+
Y 3b
NH
+
-NH 4b
In contrast with the styrene reaction, hydrogenation of 1-pentene extensively proceeded. In addition, N-methylcyclohexylamine was also formed in 16% yield (based on the &cyanide charged) presumably through hydrogenation of the isocyanide. There are several papers reporting homogeneous hydrogenation of isocyanide [4]. However, pentene reactions by the present procedure were usually more or less accompanied by precipitation of insoluble species. At the moment, we cannot unequivocally decide whether the hydrogenation of the isocyanide was homogeneously or heterogeneously catalyzed. It is interesting to note that the present reaction bears a seeming resemblance in regioselectivity to hydroformylation. Thus, the selective *The aldimine la: IR (neat) 1665 cm-r (C=N); ‘H NMR (CDC13, TMS); 6 1.0 - 1.9 (m, 10 H, (CHz)s), 1.41 (d, J= 7 Hz, 3H, CHs), 2.75 - 3.10 (m, lH, N-CH), 3.60 (dq, lH, CeHsCfI), 7.17 - 7.36 (m, 5H, CeHs), 7.67 ppm (d, J= 6 Hz, lH, CH=N); MS m/e (relative intensity) 215 (8, M+), 172 (6), 132 (5), 110 (42), 105 (23), 83 (100). **The aldimine lb: IR (neat) 1662 cm-’ (C=N); ‘H NMR (CDC13, TMS); 6 0.88 (t, J= 7 Hz, 3H, CXsCH2), 1.00 (3H, d, 5=7 Hz, CFIsCH), 1.10-1.85 (m, 14H, CHsCFIzCI& and CH2 groups in the cyclohexane ring), 2.05 - 2.45 (m, lH, CHCH=N), 2.65 - 3.05 (m, lH, CHN=), 7.42 ppm (d, J = 6 Hz, lH, CH=N); MS m/e (relative intensity) 181 (1.6, M+), 180 (l), 152 (17), 139 (92), 110 (37), 96 (58), 83 (58), 58 (85), 55 (loo), 41 (97). The aldimine 2b: IR (neat) 1666 cm-l (C=N); ‘H NMR (CDC13, TMS); 6 0.9 (t, J= 7 HZ, 3H, CHs), 1.0 - 2.0 (m, 16H, CH3CEI2CH2CfI2 and CH2 groups in the cyclobexane ring), 1.25 (m, 2H, CHzC=N), 2.90 (m, lH, CHN=), 7.68 ppm (t, J= 5 Hz, lH, CH=N); MS m/e (relative intensity) 181 (0.2, M+), 180 (0.2), 138 (8), 125 (14). 110 (13), 83 (lo), 82 (21), 56 (16), 55 (34), 44 (100).
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formation of la in the reaction of styrene stems from preferential attack of ruthenium species on the inner olefinic carbon followed by migratory insertion of isocyanide in the resulting alkylruthenium complex. This is very similar to the preferential formation of the branched aldehyde usually encountered in hydroformylation of styrene catalyzed by ruthenium [5] or other catalysts [6]. Likewise, the regioisomeric ratio in the reaction of pentene is also similar to that reported for ruthenium-catalyzed hydroformylation of l-pentene [ 51. In pentene reactions, [(PPh,),N][HRu,(CO),,] (the total yield of lb, Zb, 3b, and 4b = 18.4%) and Ru(CO),(PPh,), (the total yield = 10.4%) could also be used as the catalyst, the latter being slightly less active. Typical hydroformylation catalysts such as Rh4(C0)i2, CO,(CO)~ and HRh(CO)(PPha)s showed very little activity, the total yield being less than 0.1%. and HPt(SnC13)(PPh3), were totally inactive. In Pes(C0) 12y RuCl,(PPh,), any event, the catalyst performance in the present reactions is still low as compared with hydroformylation. This may be associated with isocyanides being stronger u-donors, which hinder the generation of a vacant coordination site required for the occurrence of the reaction. Search for more efficient catalysis is under way. References 1 B. Corn&, in J. FaIbe (ed.), New Syntheses with Carbon Monoxide, Springer-Verlag, Berlin, 1980, p. 1. 2 E. Singleton and H. E. Oosthuizen, Adv. Organometall. Chem., 22 (1983) 209. 3 H. F. Schultz and F. Bellstedt, Znd. Eng. Chem., Prod. Res. Dev., 12 (1973) 176; M. Bianchi, G. Menchi, P. Frediani, U. Matteoli and F. Piacenti, J. Organometall. Chem., 247 (1983) 89. 4 E. Band, W. R. Pretzer, M. G. Thomas and E. L. Muetterties, J. Am. Chem. Sot., 99 (1977) 7380; E. L. Muetterties, E. Band, A. Kokorin, W. R. Pretzer and M. G. Thomas, Znog. Chem., 19 (1980) 1552; S. T. McKenna, R. A. Anderson and E. L. Muetterties, Organometallics, 5 (1986) 2233. 5 T. Hayashi, Z. H. Gu, T. Sakakura and M. Tanaka, J. Organometall. Chem., 352 (1988) 373. 6 T. Hayashi, M. Tanaka and I. Ogata, J. Mol. Catal., 13 (1981) 323 and references cited therein.