Cyclohexenylboration of Aldehydes and Ketones with the Borabicyclo[3.3.2]decanes (BBDs)
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- 作者：Eduvigis Gonz谩lez ; Lorell Mu帽oz-Hern谩ndez ; Eyleen Alicea ; Bakthan Singaram ; George W. Kabalka ; John A. Soderquist
- 刊名：Organic Letters
- 出版年：2015
- 出版时间：September 4, 2015
- 年：2015
- 卷：17
- 期：17
- 页码：4368-4371
- 全文大小：355K
- ISSN：1523-7052
文摘
Asymmetric hydroboration of 1,3-cyclohexadiene with 4R produces the allylborane 5RR as essentially a single diastereomer (i.e., no observable 5RS), and its addition to representative aldehydes provides 9RS (52鈥?5%) with excellent selectivity (94鈥?9% ee). By contrast, a similar sequence with the 10-Ph-BBD reagent, 14R, results in a ca. 45:55 mixture of 15RR and 15RS. However, their addition to methyl ketones provides the corresponding 3掳-homoallylic alcohols (18RS) with excellent selectivity (80鈥?9% ee) but in low yields (15鈥?2%) because 15RS is unreactive toward either allylboration or isomerization to 15RR. Thus, with 2 equiv of 15, the yield of 18 (R = Ph) is increased from 52% to 85%. Boranes 5SS and 15SS provide enantiomeric alcohols.