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A three‐component Pd‐catalyzed coupling of ynamides, aryl diazonium salts, and aryl boronic acids for the synthesis of novel triaryl‐substituted enamides is described. This transformation represents the first example of an umpolung regioselective unsymmetrical syn‐1,2‐diarylation/aryl‐olefination of ynamides. The aryl moieties of the diazonium salt (electrophile) and boronic acid (nucleophile) are explicitly incorporated in the electrophilic α‐ and nucleophilic β‐position, respectively, of the ynamide, resulting in a single isomer of the N‐bearing tetrasubstituted olefin. The scope is broad (68 examples), showing excellent functional‐group tolerance. DFT calculations substantiate the rationale of the mechanistic cycle and the regioselectivity. The chemoselectivity and synthetic potential of the enamide products were also studied.

We herein demonstrated a N-hydroxyphthalimide (NHPI)-mediated chemo-and regioselective radical cyclization of yne-dienone with thiols to construct 3-thioaryl bearing [6,6]-fused dihydrochromenone derivatives. This transformation tolerates common functional groups and has broad scope. The reaction proceeds via the attack of a thioaryl radical to alkyne over the activated Michael acceptor. The TEMPO quenching experiment suggests the involvement of a radical intermediate. Synthetic versatility of 3-thioaryldihydrochromenones is also showcased. R adical cascades are synthetically valuable as these strategies have largely been applied for the construction of complex molecular frameworks from readily accessible precursors. 1 Notably, mild reaction conditions of the radical processes are compatible with common functional groups and are therefore synthetically viable. In general, the intramolecular radical cascades are feasible over the intermolecular processes. 1b Eventually, the cascade annulations via intermolecular radical addition to the double bond (i.e., CC, CN, and/or CO) are well exhibited; 2 on the other hand, further investigations are needed to examine the identical transformation with triple bonds (CC or CN). 3 The yne-tethered-dienones I demonstrate unequivocal importance in chemistry as these moieties are amenable to diverse annulations and synthesis of novel structural entities. 4 Some noteworthy transformations constitute the transitionmetal-catalyzed arylative/borylative/silylative/reductive and acetate-triggered cyclization of alkynyl cyclohexadienones (Scheme 1a). 5,6 Most of these cascade annulations primarily happen via nucleophile-assisted 5-exo-trig cyclization, providing [5,6]-fused heterocycles II (Scheme 1a). A rare demonstration of sulfonylative radical cyclization of alkynyl cyclohexadienone under the photoredox Ir catalysis leads to [6,6]-fused 3-sulfonylated dihydrochromenone heterocycle III (Scheme 1a). 7 Thus, expensive transition metal catalysts and harsh reaction conditions are essential for the cyclization of alkynyl cyclohexadienones, which limits wide synthetic applications. Despite these challenges, the development of metal-free intermolecular radical cyclization of yne-cyclohexadienone I to [6,6]-fused dihydrochromenone is a worthwhile endeavor (Scheme 1b).Inspired by the heteroatom-radical-mediated cyclization of an unsaturated system, 8 we envisioned examining a thioarylradical-promoted cyclization diversity with the alkynyl cyclohexadienone. We hypothesized a N-hydroxyphthalimide (NHPI)-mediated attack of the thioaryl radical to alkyne followed by intramolecular cyclization with the cyclohexadienone would result in [5,6]-fused thioaryl tetrahydrobenzofuranone (V) and/or [6,6]-fused thioaryldihydrochromenone (VII) derivatives (Scheme 1b). We consider the radical attack to alkyne would be regioselective, preferably forming Int-VI (aryl-stabilized vinyl radical) over Int-IV (alkyl-bearing vinyl radical). Next, the 6-exo-trig vinyl radical cyclization of Int-VI with the enon...

Demonstrated herein is an Au I -catalyzed annulation of sulfonyl-protected ynamides with substituted 1,2benzisoxazoles for the synthesis of E-benzo[e][1,3]oxazine derivatives. The transformationi nvolves the addition of benzisoxazole to the gold-activated ynamide, ring expansiono f the benzisoxazole fragment to provide an a-imino vinylic gold intermediate, and 1,2-migrationo ft he sulfonamide motif to the maskedc arbene center to deliver the respective ring-expanded benzo[e][1,3]oxazine of predominant E configuration. At rapping experiment justifiest he participation of the a-imino maskedg old carbene. DFT computations also support the hypothesized mechanisma nd rationalize the product stereoselectivity.[b] Prof.