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Polar reactive organometallic species have been key reagents in synthesis for more than a century. Stereodefined 1, 2-dimetallated alkenes offer promising synthetic utility; however, few methods are available for their preparation due to their relatively low stability. Here we report the reductive anti-1, 2-dimetallation of alkynes to stereoselectively generate trans-1, 2-dimagnesio- and 1, 2-dialuminoalkenes, which are stable and have been demonstrated in organic synthesis. These stereodefined 1, 2-dimetallated alkenes are prepared through the use of a sodium dispersion as a reducing agent, and organomagnesium and organoaluminium halides as reduction-resistant electrophiles. Highly nucleophilic 1, 2-dimagnesioalkenes serve as dual Grignard reagents and have been demonstrated to react with various electrophiles to afford anti-difunctionalized alkenes. The 1, 2-dialuminoalkenes react with paraformaldehyde with dearomatization of the aryl moieties to form the corresponding dearomatized 1, 4-diols, with the overall reaction being regarded as alkynyl-directed dearomatization of arenes. X-ray crystallographic analysis further supports the formation of trans-1, 2-dimagnesio- and 1, 2-dialuminoalkenes, with computational studies providing insight into the mechanism of dearomative difunctionalization.

Biaryl synthesis continues to occupy a central role in chemical synthesis. From blockbuster drug molecules to organic electronics, biaryls present numerous possibilities and new applications continue to emerge. Transition-metal-catalyzed coupling reactions represent the gold standard for biaryl synthesis and the mechanistic steps, such as reductive elimination, are well established. Developing routes that exploit alternative mechanistic scenarios could give unprecedented biaryl structures and expand the portfolio of biaryl applications. We have developed metal-free C–H/C–H couplings of aryl sulfoxides with phenols to afford 2-hydroxy-2′-sulfanylbiaryls. This cascade strategy consists of an interrupted Pummerer reaction and [3, 3] sigmatropic rearrangement. Our method enables the synthesis of intriguing aromatic molecules, including oligoarenes, enantioenriched dihetero[8]helicenes, and polyfluorobiaryls. From our successes in aryl sulfoxide/phenol couplings and a deeper understanding of sigmatropic rearrangements for biaryl synthesis, we have established related methods, such as aryl sulfoxide/aniline and aryl iodane/phenol couplings. Overall, our fundamental interests in underexplored reaction mechanisms have led to various methods for accessing important biaryl architectures.

The reduction of styrenes with lithium arenide in a flow microreactor leads to the instantaneous generation of highly unstable radical anions that subsequently dimerize to yield the corresponding 1, 4-organodilithiums. A flow reactor with fast mixing is essential for this reductive dimerization as the efficiency and selectivity are low under batch conditions. A series of styrenes undergo dimerization, and the resulting 1, 4-organodilithiums are trapped with various electrophiles. Trapping with divalent electrophiles affords precursors for useful yet less accessible cyclic structures, for example, siloles from dichlorosilanes. Thus, we highlight the power of single-electron reduction of unsaturated compounds in flow microreactors for organic synthesis.