Cooperative Iodide Pd(0)‐Catalysed Coupling of Alkoxyallenes and N‐Tosylhydrazones: A Selective Synthesis of Conjugated and Skipped Dienes

Abstract

Palladium(0)-catalysed hydro-alkylation or -alkenylation of alkoxyallenes with N-tosylhydrazones gives direct access to conjugated and skipped 1-alkoxydienes with high efficiency and excellent functional-group compatibility. The reaction is proposed to involve the in situ-formed t-butanol as proton source in the key step of the allylpalladium(II) species generation. Moreover, lithium iodide or iodobenzene are employed as an unprecedented iodide (I ) reservoir to sustain the catalytic cycle.

Palladium-Catalyzed Regio- and Stereoselective Synthesis of (E)-1,3-Bissilyl-6-arylfulvenes from Aryl Iodides and Silylacetylenes

“…Other metal iodides and TBAI were not effective, and the yield of 3a did not exceed 68% (entries 12 vs 16−18). Although the role of NaI is not clear in this stage, it is possible that the NaI stabilizes the Pd species in situ 15 during the long reaction period. Next, the reaction time was scrutinized (entries 19−21).…”

Hydroarylation of N‐Allenyl Derivatives Catalyzed by Copper**

“…Hydrofunctionalization of allenes mainly allowed the selective formation of C–N, C–O, and C–C bond. [ 2,3,5–8 ] The latter being performed through the addition of pronucleophiles such as malonates, [ 9–12 ] nitriles, [ 13–16 ] alkynes, [ 17–19 ] alkenes, [ 20–22 ] and aryl derivatives. The reaction of aromatic compounds with allenes, known as hydroarylation reaction, consists of adding an aryl moiety to a C–C double bond and constitutes a powerful tool to form a Csp 3 –Csp 2 bond in a regio‐ and stereoselective manner.…”

π-Allylpalladium Complexes in Synthesis: An Update

“…In 2018, we reacted alkoxyallenes 185 with N-tosylhydrazones 186 to selectively afford 1,3-188 and 1,4-dienes 187 depending on the starting N-tosylhydrazone. 75 When diaryl-N-tosylhydrazones were used, conjugated dienes were obtained, while aryl-alkyl-N-tosylhydrazones afforded the 'kinetic' skipped 1,4-dienes (Scheme 55). Iodide was compulsive to regenerate the active Pd(0) species and to allow the coupling, given the absence of starting materials containing the halogen useful to conclude the catalytic cycle by HI elimination.…”