Cascade Multicomponent Assemblies Involving 1,3-Enynes via Auto-Tandem Palladium Catalysis

Abstract

Here we report a three-component auto-tandem reaction of 1,3-enyne-tethered carbonyls, organoboronic reagents, and suitable nucleophiles catalyzed by palladium, proceeding through consecutive intramolecular vinylogous addition, Suzuki coupling, and allylic alkylation. This process exhibited high chemo- and regioselectivity with 1,3,4-trifunctionalization of the 1,3-enyne motif, and a wide range of 2H-chromenes, 1,2-dihydroquinolines, benzo­[b]­oxepines, 1,7-annulated indoles, and other frameworks were efficiently constructed in fair to good yields and E/Z selectivity.

A syn outer-sphere oxidative addition: the reaction mechanism in Pd/Senphos-catalyzed carboboration of 1,3-enynes

“…In our recently reported trans -hydroboration 15 and trans -cyanoboration 16 of 1,3-enynes catalyzed by a Pd 0 /Senphos ligand complex, an unusual “outer-sphere” oxidative addition mechanism featuring a Pd-π-allyl intermediate is proposed. 17,18 Our initial mechanistic hypothesis was analogous (Scheme 2a): the presence of Senphos ligand L enables (COD)Pd(CH 2 TMS) 2 to reductively eliminate 1,2- bis(trimethylsilyl)-ethane to form the active LPd 0 species I , 19 which then binds to the 1,3-enyne. The resulting LPd 0 –enyne complex II is then activated by the Lewis acidic C–boron enolate to furnish the outer-sphere oxidative adduct III .…”

Efficient synthesis of 3‐sulfonyl‐1,2‐dihydroquinolines via tandem aza‐Michael addition/cyclizations of N‐acyl‐protected 2‐aminobenzaldehyde with vinyl sulfones

“…Some representative biologically active molecules and pharmaceuticals containing 1,2-dihydroquinoline motifs are shown in Figure 1. Therefore, the development of effective and advanced methodologies for the synthesis of 1,2-DHQs continues to be an extremely vibrant field of research [16][17][18][19][20][21]. Consequently, numerous synthetic strategies have been developed for their construction [22][23][24][25][26][27][28][29][30][31][32][33].…”