HOTf-Catalyzed Alkyl-Heck-type Reaction

Abstract

SummaryThe Heck reaction, along with other cross-coupling reactions, led to a revolution in organic chemistry. In the last 50 years, metal-catalyzed, photo-induced, or base-mediated Heck and Heck-type reactions have been elegantly developed. Brønsted acid-catalyzed Heck (or Heck-type) reactions are still unknown, however. By introducing alkyl peroxides as the key intermediates, primary, secondary, and tertiary aliphatic carboxylic acids are therefore applied here in a one-pot Brønsted acid-catalyzed Heck-type reaction, to deliver E-alkenes exclusively in most cases. The use of HOTf is vital to the reaction, whose mechanism is supported by both experimental and computational results. This method can be expanded to the direct alkylation of complex natural products.

Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel

“…In contrast, alkyl-Heck-type reactions were much more challenging and rarely explored until the last decade. Pioneered by Oshima 26 and Fu's seminal works 27 , effective strategies have been developed to facilitate this alkenylations with simple alkyl halides as electrophiles [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] . Notably, two elegant palladium-catalyzed cases involving alkyl C-H activation were disclosed by the groups of Yu 45 and Sanford 46 , which employed N-arylamide or pyridine as a neighboring directing group with stoichiometric amounts of external oxidant.…”

Iron‐Catalyzed Vinylic C−H Alkylation with Alkyl Peroxides

“…We performed control experiments to probe the mechanism of the reaction. It is worth noting that this coupling reaction could also be promoted by HOTf, but the reaction rates of the conversion of styrenes into the alkylated styrenes catalyzed by 5 mol % Fe(OTf) 3 were much fast than that promoted by 20 mol % HOTf. These results suggest that a catalytic amount of HOTf generated from Fe(OTf) 3 is not responsible for the reaction rates, and thus, the iron metal is the real catalyst species (Figures S1 and S2 in the Supporting Information).…”

Copper-catalyzed 1,4-alkylarylation of 1,3-enynes with masked alkyl electrophiles

“…Our previous studies revealed that alkyl peroxides generated from the corresponding alkyl carboxylic acids, can in the presence of a copper, 13 iron 12 and HOTf 14 catalyst act simultaneously as alkylating reagents and internal oxidants. Actually, the alkyl diacyl peroxides in a catalytic system can be simply regarded as masked alkyl electrophiles ( Fig.…”