Hindered organoboron groups in organic chemistry. 25. The condensation of aliphatic aldehydes with dimesitylboryl stabilised carbanions to give alkenes.
作者:Andrew Pelter、Keith Smith、Said M.A. Elgendy
DOI:10.1016/s0040-4020(01)87983-7
日期:1993.8
In the presence of protic acids the condensation of aliphatic aldehydes with dimesitylboryl stabilised carbanions results in alkenes. In the presence of strong acids such as HCl or CF3SO3H, the products contain > 90% of E-alkenes in all cases tried. When acetic acid is used, then Z-alkenes may result predominantly, particularly in the cases of RsCHO and RtCHO. HX HCI, CF3SO3H gives E - alkenes in
在质子酸的存在下,脂族醛与二聚三苯甲基稳定的碳负离子的缩合会生成烯烃。在强酸(例如HCl或CF 3 SO 3 H)的存在下,在所有尝试的情况下,产品均含有> 90%的E-烯烃。当使用乙酸时,则可能主要产生Z-烯烃,特别是在R s CHO和R t CHO的情况下。在所有情况下,HXHCl,CF 3 SO 3 H均会生成E-烯烃。HXCH 3 CO 2 H,使得主要ž -烯烃当Rř秒,R叔。
Hindered organoboron groups in organic synthesis. 14. stereoselective synthesis of alkenes by the boron-wittig reaction using aliphatic aldehydes
In the presence of HX, carbanions Mes2BCHLiR1 react with aliphatic aldehydes to give alkenes. The stereochemistry of the product alkene depends upon the nature of HX.
Hindered organoboron groups in organic chemistry. 24. The condensation of aliphatic aldehydes with dimesitylboron stabilised carbanions to give ketones.
作者:Andrew Pelter、Keith Smith、Said M.A. Elgendy、Martin Rowlands
DOI:10.1016/s0040-4020(01)87982-5
日期:1993.8
The condensation of boron stabilised carbanions, Mes2BCHLiR1, (R1≠H) with aliphatic aldehydes, R2CHO, followed by treatment with trifluoroacetic anhydride (TFAA) or N-chlorosuccinimide (NCS) is an unique, broadly applicable redox process that yields ketones, R1CH2COR2, directly and in high yields. The anion Mes2BCH2Li (Mes2BCHLiR1, R1H) gives high yields of alkenes, R2CHCH2 in the same conditions
The dimesitylboron group in organic synthesis 8. Preparations of 1,3-diols from oxiranes
作者:Andrew Pelter、Gina Bugden、Richard Rosser
DOI:10.1016/s0040-4039(01)80862-5
日期:1985.1
Alkyldimesitylboranes, yield anions1, Mes2BCHR, that on reaction with oxiranes followed by oxidation give 1,3-diols. These anions are thus the operational equivalent of RCHOH. The scope and limitations of the new process are delineated.
Hindered organoboron groups in organic chemistry. 23. The interactions of dimesitylboron stabilised carbanions with aromatic ketones and aldehydes to give alkenes.
Dimesitylboron stabilised carbanions react with diarylketones to give the corresponding alkenes in mild conditions with good yields. Reactions with aromatic aldehydes are more complex, but in all cases E-alkenes are available in good yields by trapping the intermediates with chlorotrimethylsilane followed by treatment with aq. HF/CH3CN. Treatment of the same intermediates with trifluoroacetic anhydride