Iron Compounds in Organic Synthesis

Abstract

The title compound adds to R,-unsaturated carbonyls to give the products of 1,4-addition after hydrolysis of the intermediate boron enolates, in 68-86% isolated yield (four examples). In addition, we discovered that diazomethane reacts with bis(pinacola-to)diborane to insert methylene to give (pinacolato) 2 BCH 2 B in 83% yield. An alternative synthesis involved coupling of (pinacolato)BCH 2 I with various metals. Boronic acids have a variety of important uses and applications. They are highly valued synthetic inter-mediates 1 and also possess significant biological activity. 2 Hydroboration, 3 haloboration, 4 reactions with or-ganometallics, 5 and homologation 6 are important protocols for their preparation. A more recent and very convenient method for the preparation of boronic acids involves diborane(4) derivatives. 7 In particular, tet-raalkoxydiborane(4) compounds have been shown to add to alkenes, 8 alkynes, 9 1,3-butadienes, 10 allylic acetates, 11 methylenecyclopropanes, 12 substituted 4-arylbut-3-en-2-ones, 13 and various other substrates. 14 Mechanistic and theoretical studies of diboration have also been reported. 15 The latter reaction reported by Marder and Norman et al. is particularly interesting, in that it opens the way for addition of diborane(4) compounds to other R,-unsaturated systems. Three-membered 16 and five-membered 17 aminodiborane(4) derivatives undergo insertion reactions with CO and isonitrile to give inter-† Hebrew University in Jerusalem. ‡ Tel-Aviv University. (1) Pelter, A.; Smith, K.; Brown, H. C. Borane Reagents. In Best Synthetic Methods; Katritzky, A. R., Meth-Cohn, M., Rees, C. W., Eds.; Academic Press: London, 1988. (2) (a) For a review of biologically active boron analogues, see: Morin, C. Tetrahedron 1994, 50, 12521. (b) For the use of boranes in boron neutron capture therapy, see: Soloway, A. H.; Tjarks, W.; barnum, B. A.; Rong, F.-G.; Barth, R. F.; Codogni. I. M.; Wilson, J. G. Chem. Rev. 1998, 98. 1515. (3) Brown, H. C.; Ramachandran, P. Marder, T. B. Chem. Commun. 1998, 1983. (g) Baker, R. T.; Nguyen, P.; Marder, T. B.; Wescott, S. A. Angew. Chem., Int. Ed. Engl. 1995, 34, 1336. (9) (a) Ishiyama, T.; Matsuda, N.; Murata, M.; Ozawa, F.; Suzuki, A.; Miyaura, N. Organometallics 1996, 15, 713. (b) Hiyama, T.; Yamamoto, M.; Miyaura, N. Chem. Lett. 1996, 1117. (c) Lesley, G.; Nguyen, P.; Taylor, N. J.; Marder, T. B.; Scott, A. J.; Clegg, W.; Norman, N. C. Organometallics 1996, 15, 5137. (d) Ishiyama, T.; Matsuda, N.; Miyaura, N.; Suzuki, A. Lesley, M. J. G.; Norman, N. C.; Orpen, A. G.; Starbuck, J. New J. Chem. 1999, 23, 1053. (g) Suginome, M.; Matsuda, T.; Ito, Y. Organometallics 1998, 17, 5233. Boryl alkynes: (h) Bluhm, M.; Maderna, A.; Pritzkow, H.; Bethke, S.; Gleiter, R.; Siebert, W. Eur. J. Inorg. Chem. 1999, 1693. (10) (a) Ishiyama, T.; Yamamoto, M.; Miyaura, N. Chem. Commun. 1996, 2073. (b) Clegg, W.; Johann, T. R. F.; Marder, T. B.; Norman, N. C.; Orpen, A. G.; Peakman, T. M.; Quayle, M. J.; Rice, C. R.; Scott, A. J. Lesley, M. J. G.; Marder, T. B.; Norman, N. C.; Rice, C. R. Chem. Commun. 1997, 2051. (14) Aryl halides: (a): Ishiyama, T.; Itoh, Y.; Kitano, T.; Miyaura, N. Tetrahedron Lett. 1997, 38, 3447. Imines: (b) Mann, G.; John, K. D.; Baker, R. T. Org. Lett. 2000, 2, 2105. (c) Cameron, T. M.; Baker, R. T.; Wescott, S. A. Chem. Commun. 1998, 2395. Hydrazines: (d) Hommer, H.; Nöth, H.; Sachdev, H.; Schmidt, M.; Schwenk, H.; Chem. Ber. 1995, 128, 1187. Carbenoids: (e) Hata, T.; Kitagawa, H.; Masai, H.; Kurahashi, T.; Shimuzu, M.; Hiyama, T. Angew. Chem., Int. Ed. 2001, 40, 790. (15) Mechanism: (a) Clark, G. R.; Irvine, G. J.; Roper, W. R.; Wright, L. J. Organometallics 1997, 16, 5499. (b) Dai, C.; Stringer, G.; Marder, T. B.; Scott, A. J.; Clegg, W.; Norman, N. C. Inorg. Chem. 1997, 36, 272. (c) Marder, T. B.; Norman, N. C.; Rice, C. R.; Robins, E. G. Chem. Commun. 1997, 53. (d) Irvine, G. J.; Lesley, M. J. G.; Marder, T. B.; Norman, N. C.; Rice, C. R.; Robins, E. G.; Roper, W. R.; Whittell, G. R.; Wright, L. J. Chem. Rev. 1998, 98, 2685. (e) Clegg, W.; Lawlor, F. J.; Marder, T. B.; Nguyen, P.; Norman, N. C.; Orpen, A. G.; Quayle, M. J.; Rice, C. R.; Scott, A. J.; Souza, F. E. S.; Stringer, G.; Whittell, G. R. J. Chem. Soc., Dalton Trans. 1998, 301. Theoretical studies on alkenes and alkynes: (f) Cui, Q.; Musaev, D. G.; Morokuma, K.