Alkaloid from alkyl halides

Intermediate samarium enolates derived from ketones 1522 or 1525 could stereoselectively be trapped with allyl halides, leading to tricycles 1524 and 1526. The intramolecular alkylation by the chloroalkyl terminus of compound 1527 led to tetracyclic compound 1528 with satisfactory efficiency. These cascade reactions selectively generate three continuous stereogenic centers, including a quaternary carbon atom at the 3-position of the dihydroindole moiety, a structural motif of many indole alkaloids. 

Reduction of an alkylmercury halide or acetate with a borohydride provides an alternative method for accessing a carbon radical species (see Scheme 4.11). The alkylmercury compound can be prepared by one of a number of methods, such as from the corresponding Grignard reagent or from addition of Hg(OAc)2 to an alkene. For example, intramolecular amido-mercurafion of the alkene 50, followed by formation of the alkyl radical and addition to methyl acrylate provides a route to the alkaloid 8-coniceine (4.46). ... 

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