of the organometallic variety, namely organomagnesium, -zinc, -tin, -silicon, and –boron. Combined with electrophilic aryl halides, N-tosylhydrazones can be used to prepare polysubstituted olefins under Pd-catalyzed conditions without the use of often expensive, and synthetically demanding organometallic reagents. The scope of the reaction is wide; N-tosylhydrazones derived from aldehydes and ketones are well tolerated, which leads to both di- and trisubstituted olefins. Moreover, and variety of aryl halides are well tolerated as coupling partners including those bearing both electron-withdrawing and electron-donating groups, as well as π-rich and π-deficient aromatic heterocyclic compounds. Stereochemistry is an important element to consider when preparing polysubstituted olefins. Using hydrazones derived from linear aldehydes resulted in exclusively trans olefins, while the stereochemical outcomes of trisubstituted olefins were dependent on the size of the substituents. The mechanism of this transformation is thought to proceed in a manner similar to the synthesis of alkenes through the Bamford–Stevens reaction; the decomposition of N-tosylhydrazones in the presence of base to generate diazocompounds which then release nitrogen gas, yielding a carbene, which then can be quenched with an electrophile. In this case, the coupling reaction starts with the oxidative addition of the aryl halide to Pd0 catalyst to give the aryl PdII complex. The reaction of the diazocompound, generated from the hydrazone, with the PdII complex produces a Pd-carbene complex. A migratory insertion of the aryl group gives an alkyl Pd complex, which undergoes syn beta-hydride elimination to generate the trans aryl olefin and regenerate the Pd0 catalyst. This reaction has also seen utility in preparing conjugated enynes from N-tosylhydrazones and terminal alkynes under similar Pd-catalyzed reaction conditions and following the same mechanism. Moreover, Barluenga and coworkers demonstrated a one-pot three-component coupling reaction of aldehydes or ketones, tosylhydrazides, and aryl halides in which the N-tosylhydrazone is formed in situ. This process produces stereoselective olefins in similar yields compared to the process in which preformed N-tosylhydrazones are used. Barluenga and coworkers also developed metal-free reductive coupling methodology of N-tosylhydrazones with boronic acids. The reaction tolerates a variety of functional groups on both substrates, including aromatic, heteroaromatic, aliphatic, electron-donating and electron-withdrawing substituents, and proceeds with high yields in the presence of potassium carbonate. The reaction is thought to proceed through the formation of a diazo compound that is generated from a hydrazone salt. The diazo compound could then react with the boronic acid to produce the benzylboronic acid through a boronate intermediate. An