The hydroboration of 3-butenyl derivatives with 9-borabicyclo[3.3.1]nonane |
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Authors: | Jackson Chi-San Chen |
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Institution: | Richard B. Wetherill Laboratory, Purdue University, West Lafayette, Indiana 47907 U.S.A. |
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Abstract: | The hydroboration of 3-butenyl derivatives, CH2CHCH2CH2X where X represents OH, OMe, OAc, Cl, as well as the related carboxylic ester, CH2CHCH2COOEt, and the nitrile CH2CHCH2CN, with 9-borabicyclo3.3.1]nonane (9-BBN) proceeds with remarkably high regio-selectivity. The boron is placed essentially on the terminal carbon (?98%), yielding stable organoboranes which can be readily oxidized to alcohols or subjected to other reactions. The yields of alcohols in the hydroboration-oxidation procedure are satisfactory, in the range of 82–99%. The hydroxy group liberates hydrogen rapidly and quantitatively but no further reaction is observed and hydroboration of the carboncarbon double bond then proceeds normally. The chloro and methoxy groups are not affected by 9-BBN, whereas, the ester and nitrile groups are slightly (1.5–4.0%) reduced by the reagent at 25°C. Even this small amount of reduction can be circumvented or minimized by carrying out the hydroboration at 0°C. Although this procedure requires somewhat longer reaction times, the products are cleaner and the yields are higher. |
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