A Cs 2 CO 3 -mediated [2 + 1] cycloaddition of benzofuran-derived azadienes (BDAs) with bromomalonate by using a dearomatization strategy has been developed. Through this process, BDAs serve as a potential 2-atom synthon in the construction of a range of functionalized spirocyclopropane derivatives, such as spirobenzofuran-2-cyclopropanes and spiroindane-2-cyclopropanes.
An unusual [2 + 3]
cycloaddition of isatin azomethine imines (AIs)
and in situ generated azaoxyallyl cations has been developed. It is
the first example where AIs serve as the [C,O] 2-atom synthon in organic
synthesis. This work not only reveals a new role of isatin AIs in
cycloaddition reaction but also provides an efficient access to unprecedented
spiroheterocycle compounds.
A Cs2CO3-mediated formal [4+3] cycloaddition involving benzofuran-derived azadienes (BDAs) and α‑bromohydroxamates to afford benzofuran-fused 1,4-diazepinones is established. This is the first example of using BDAs for the construction of seven-membered...
Activated alkyl halides have been extensively explored to generate alkyl radicals with Ru‐ and Ir‐ photocatalysts for 1,2‐difunctionalization of alkenes, but unactivated alkyl bromides remain challenging substrates due to their strong reduction potential. Here we report a three‐component 1,2‐difunctionalization reaction of alkenes, unactivated alkyl bromides and nucleophiles (e.g., amines and indoles) using a trinuclear gold catalyst [Au3(tppm)2](OTf)3. It can achieve the 1,2‐aminoalkylation and 1,2‐alkylarylation readily. This protocol has a broad reaction scope and excellent functional group compatibility (>100 examples with up to 96 % yield). It also affords a robust formal [2+2+1] cyclization strategy for the concise construction of pyrrolidine skeletons under mild reaction conditions. Mechanistic studies support an inner‐sphere single electron transfer pathway for the successful cleavage of inert C−Br bonds.
In this review, photoinduced activation of unactivated alkyl chlorides via single electron transfer strategy, chlorine atom transfer, metallaphotoredox synergistic catalysis, and photoexcited metal catalysis strategies have been discussed.
A divergent reaction of indoline-derived azadienes with α-bromohydroxamates for the selective synthesis of spiro-indolinepyrrolidinones and indoline-fused diazepinones was disclosed. This reaction sequence involved an initial formation of five-membered spirocyclic products followed by an intramolecular ring-opening and ring expansion to produce seven-membered diazepinones. We demonstrated that controlling the reaction time could modulate the reaction pathway for formation of different molecular frameworks for the same set of substrates. Based on the experimental results, the reaction mechanism was also discussed and proposed to explain the phenomena observed in the process.
Activated alkyl halides have been extensively explored to generate alkyl radicals with Ru‐ and Ir‐ photocatalysts for 1,2‐difunctionalization of alkenes, but unactivated alkyl bromides remain challenging substrates due to their strong reduction potential. Here we report a three‐component 1,2‐difunctionalization reaction of alkenes, unactivated alkyl bromides and nucleophiles (e.g., amines and indoles) using a trinuclear gold catalyst [Au3(tppm)2](OTf)3. It can achieve the 1,2‐aminoalkylation and 1,2‐alkylarylation readily. This protocol has a broad reaction scope and excellent functional group compatibility (>100 examples with up to 96 % yield). It also affords a robust formal [2+2+1] cyclization strategy for the concise construction of pyrrolidine skeletons under mild reaction conditions. Mechanistic studies support an inner‐sphere single electron transfer pathway for the successful cleavage of inert C−Br bonds.
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