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. 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
Hindered organoboron groups in organic chemistry. 20. Alkylations and acylations of dimesitylboron stabilised carbanions
作者:Andrew Pelter、Lorraine Warren、John W. Wilson
DOI:10.1016/s0040-4020(01)80393-8
日期:1993.4
The alkylation of carbanions derived from alkyldimesitylboranes is an efficient process leading to prim-RBMes2, sec-RBMes2 and tert-RBMes2, all of which can be derived from MeBMes2. Subsequent oxidation gives a general synthesis for prim-ROH. Secondary alkanols are also produced on oxidation, but the release of t-alkanols has not been accomplished in an efficient fashion. Studies are given of the acylation
Stereoselective synthesis of E- and Z-alkenes by the boron–Wittig reaction
作者:Andrew Pelter、Eieter Buss、Eamon Colclough
DOI:10.1039/c39870000297
日期:——
Reactions of dimesitylboryl stablised carbanions with aromatic aldehydes produce erythro-intermediates, which can be trapped by trimethylsilylation or trifluoroacetylation to give products which can yield E- or Z-alkenes in good overall yields in new and controllable boron–Wittigreactions.