Catalytic Borylations
There is an increasing demand for the organoboron compounds in organic synthesis, since a variety of useful transformation reactions of organoboronic acid derivatives have been established. We have focused our attention to the synthesis of functionalized organoboronic acid derivatives by new catalytic reactions, in which the boryl group and the functional group are introduced concomitantly. Following are the catalytic borylation reactions such as carboboration and silaboration, which we have so far established.
Direct Carboborations: Cyanoboration and Alkynylboration
Particular efforts have been devoted to carboboration, in which a boryl group and organic group are introduced to unsaturated organic molecules in one step. As the first catalytic carboboration reaction, we established palladium-catalyzed cyanoboration of carbon-carbon triple bonds using cyanoboranes [Ref .1]. We then found alkynylboration, in which the C–B bonds of alkynylboranes add to carbon-carbon triple bonds in a cis-fashion [Ref. 2]. These carboboration reactions involve activation of the B–C bond in cyanoboranes and alkynylboranes, which is followed by insertion of alkynes into the transition metal–boron bonds. The products were found to be good synthetic intermediates for highly substituted or conjugated alkenes.
Transmetallative Three-Component Carboboration
We also established transmetallative carboboration in which chloroborane and organometallic reagents such as organostannane and organozirconium were used as a source of the boryl and organic groups, respectively [intermolecular Ref. 3; cyclizative Ref. 4]. Activation of the B–Cl bond, which has never been utilized in catalytic reactions, is crucially involved in the catalysis.
Related Researches
- Intramolecular Cyanoboration
- Transmetallative Cyclizative Carboboration
- Silaboration
- Silaborative Coupling Reaction
- Intramolecular Silaboration
- Catalytic Asymmetric Silaboration
References
- Ref. 1
- Palladium- and Nickel-Catalyzed Intramolecular Cyanoboration of Alkynes M. Suginome, A. Yamamoto, M. Murakami, J. Am. Chem. Soc. 2003, 125, 6358-6359, 10.1021/ja0349195
- Palladium-Catalyzed Addition of Cyanoboranes to Alkynes Leading to Regio- and Stereoselective Synthesis of β-Boryl-α,β-unsaturated Nitriles M. Suginome, A. Yamamoto, M. Murakami, Angew. Chem., Int. Ed. 2005, 44, 2380-2382, 10.1002/anie.200462961
- Intramolecular Cyanoboration of Alkynes via Activation of Boron-Cyanide Bonds by Transition Metal Catalysts M. Suginome, A. Yamamoto, M. Murakami, J. Organomet. Chem., 2005, 690, 5300–5308, 10.1016/j.jorganchem.2005.05.005
- Reactions of Cyanoboranes with a Palladium–PMeSUB{3}; Complex: Mechanism for the Catalytic Cyanoboration of Alkynes M. Suginome, A. Yamamoto, T. Sasaki, and M. Murakami, Organometallics, 2006, 25, 2911–2913, 10.1021/om060246y
- Synthetic Application of Intramolecular Cyanoboration on the Basis of Removal and Conversion of a Tethering Group by Palladium-Catalyzed Retro-allylation T. Ohmura, T. Awano, M. Suginome, H. Yorimitsu, K. Oshima, Synlett 2008, 423-427, 10.1055/s-2008-1032075
- Ref. 2
- Nickel-Catalyzed Addition of Alkynylboranes to Alkynes M. Suginome, M. Shirakura, A. Yamamoto, J. Am. Chem. Soc. 2006, 128, 14438-14439, 10.1021/ja064970j
- Ref. 3
- Palladium-Catalyzed Carboboration of Alkynes Using Chloroborane and Organozirconium Reagents M. Daini, M. Suginome, Chem. Commun. 2008, 5224-5226, 10.1039/b809433k
- Ref. 4
- Nickel-Catalyzed trans-Alkynylboration of Alkynes via Activation of a Boron-Chlorine Bond A. Yamamoto, M. Suginome, J. Am. Chem. Soc. 2005, 127, 15706-15707, 10.1021/ja055396z
- Palladium-Catalyzed trans- and cis-Carboboration of Alkynes Tethered to Chloroborane with Organozirconium Reagents: Ligand-Dependent Complementary Stereoselectivity M. Daini, A. Yamamoto, M. Suginome, J. Am. Chem. Soc. 2008, 130, 2918-2919, 10.1021/ja711160h