Chloroborane-dioxane Complexes

ChemFiles Volume 5 Article 9

Hydroboration of various olefins using monochloroborane or dichloroborane is a common route to valuable synthetic intermediates, including amines, ketones, dienes, and boronic acids or esters.1 The most common adducts used for this transformation, monochloroborane-dimethyl sulfide or catecholborane, both suffer from significant drawbacks. Monochloroborane-dimethyl sulfide exists in equilibrium with the BH3 and BHCl2 adducts and is unpleasant to handle in large-scale applications due to the presence of dimethyl sulfide. Catecholborane reacts sluggishly with alkenes and alkynes at room temperature and requires elevated temperatures to achieve the desired product. Furthermore, isolation of the product is sometimes complicated by the presence of the catechol byproduct.

Developed in the laboratory of H.C. Brown, the mono- and dichloroborane-dioxane complexes (Figure 2) eliminate many of these issues while retaining excellent selectivity and displaying good long-term stability and low volatility. These reagents can readily substitute for common hydroborating reagents such as BH3·THF and BMS.2 Sigma-Aldrich is pleased to offer these superior reagents for research applications.

Figure 2

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Materials

     

References

  1. Brown, H. C.; Zaidlewicz, M. Recent Developments; Organic Syntheses via Boranes Series, Volume 2; Aldrich Chemical Co., Inc.: Milwaukee, 2001.
  2. (a) Kanth, J. V. B.; Brown, H. C. J. Org. Chem. 2001, 66, 5359. (b) Kanth, J. V. B.; Brown, H. C. Org. Lett. 1999, 1, 315. (c) Josyula, K. V. B. et al. Tetrahedron Lett. 2003, 44, 7789.

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