Radical Brook rearrangement (RBR) has been identified as a viable pathway in M−H (M = Co, Fe) catalyzed hydrogen-atom-transfer reactions involving unsaturated acylsilanes. Guided by the same concept, we have explored two transformations, namely, a Co-catalyzed cycloisomerization reaction and a Fe-catalyzed cyclization/Giese addition reaction. Both reactions involve the generation of a versatile α-siloxy radical intermediate via concomitant philicity inversion and radical translocation, which is mechanistically distinct from coupling reactions involving fragmentation/reduction pathways. Synthesis of cyclic silyl enol ethers and sterically congested cyclopentanol derivatives have been thus achieved with high regio-and diastereo-selectivity.

Here we report a copper-catalyzed formal dehydration polymerization of propargylic alcohols. Copper catalysis allows for efficient in situ generation of [n]cumulenes (n = 3, 5) by a soft deprotonation/β-elimination pathway and subsequent polymerization via organocopper species. Alkyne polymers (M n up to 36.2 kg/mol) were produced with high efficiency (up to 95% yield) and excellent functional group tolerance. One-pot synthesis of semiconducting head-to-head poly(phenylacetylene) was demonstrated through a polymerization−isomerization sequence.

Here we report the design, preparation, synthetic utility, and sensing application of a class of proaromatic structures, namely bicyclo[2.2.0]hexene (BCH) derivatives. Building on a valence isomerism concept, they feature modular and easy synthesis as well as high thermal stability, and can be oxidatively activated under mild conditions. New alkyl transfer reactions using BCHs as a radical donor have been developed to showcase the utility of their proaromaticity. Moreover, the redox-triggered valence isomerization of a quinoline-derived BCH led to colorimetric and fluorescent responses toward vapors of electrophilic reagents in solution and solid phase, respectively. This optical response was shown to involve a 1,3-cyclohexadiene structure that possesses an intramolecular charge transfer excited state with interesting aggregation induced emission (AIE) character. Thus, the potential of BCHs has been demonstrated as a versatile platform for the development of new reagents and functional materials.