Bronsted Acid as a Proton Donor

One year later, they discovered that Tf2NH promoted 5-endo-dig cyclization of l-siloxy-l,5-diynes, which results in the concomitant formation of carbon-halogen bonds as a result of halide abstraction from haloalkane (CHCI3, CH2Br2, CH2CI2, Mel) by intermediate alkenyl cation to afford P-halo enones as a single alkene isomer dr 97 3) (Table 2.11) [23]. Interestingly, the use of either CSA or anhydrous HCl resulted in the formation of alternative reaction products. 

Intermolecular Reaction In 2005, Bergman reported intermolecular hydroamina-tion and hydroarylation of anilines and alkenes catalyzed by a proton which is 

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