A practical method for the allylation, prenylation, propargylation, and diastereoselective crotylation of indoles has been developed using air‐ and moisture‐stable potassium organotrifluoroborate reagents (see scheme). Lewis acids such as BF3⋅Et2O promote addition to afford 2‐allyl‐ and 2‐crotylindolines in high yields and diastereoselectivities.
Aluminium dodecyl sulfate trihydrate [Al(DS)3].3H2O is easily prepared and can be used as a Lewis acid surfactant catalyst in water to conduct the highly efficient Michael addition of indoles and pyrrole to alpha,beta-unsaturated electron-deficient compounds at room temperature.
Two convenient highly diastereoselective protocols for the allylation and crotylation of ketones using practical, air- and water-stable potassium allyl and crotyltrifluoroborate salts have been developed. BF(3).OEt(2) and montmorillonite clay are used as catalysts to promote additions. The montmorillonite-catalyzed method in particular is very robust, providing a straightforward and scalable method for the allylation and crotylation of a range of ketones and aldehydes.
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