Enantioselective Lactonization by π‐Acid‐Catalyzed Allylic Substitution: A Complement to π‐Allylmetal Chemistry

Abstract

Asymmetric allylic alkylation (AAA) is a powerful method for the formation of highly useful, non-racemic allylic compounds. Here we present a complementary enantioselective process that generates allylic lactones via p-acid catalysis. More specifically, a catalytic enantioselective dehydrative lactonization of allylic alcohols using a novel Pd II -catalyst containing the imidazole-based P,N-ligand (S)-StackPhos is reported. The high-yielding reactions are operationally simple to perform with enantioselectivities up to 99 % ee. This strategy facilitates the replacement of a poor leaving group with what would ostensibly be a better leaving group in the product avoiding complications arising from racemization by equilibration.

Rhodium-catalyzed aminoacylation of alkenes via carbonylative C–H activation toward poly(hetero)cyclic alkylarylketones

“…Notably, a larger-sized cycloalkene framework perhaps shortened the distance between the amide nitrogen with the intramolecular alkenyl group and promoted the aminorhodation ( 2ah ) slightly. Conversely, the ring strain of the cyclopentene motif reduced the chance of intramolecular attack greatly and inhibited the initial cyclization ( 2ai ) completely, 18 which was confirmed when the linear α,β,γ,δ-unsaturated acylaniline was applied. However, there was little chance that nucleophilic acylaniline nitrogen could meet the tailed alkenyl in the noncyclic substrate ( 2aj ).…”

Tuning StackPhim Ligands: Applications in Enantioselective Borylation and Alkynylation

“…9,10 Recent work from our laboratory has been focused on developing 5-membered nitrogen heterocycle-based Stackligands. [11][12][13][14][15] Although many reactions work well with our parent ligand, now dubbed StackPhos, the need for tuning has arisen. Since these are 5-membered heterocycles, we identified the imidazole as a tunable element and our initial report on modified ligands involved the enantioselective alkynylation of Meldrum's acid acceptor 1 (Figure 1a).…”