Zirconocene-promoted coupling reaction of terminal acetylenes to geminal enediynes in the presence of p-chloranil

Coupling Reactions of Zirconate Complexes Induced by Carbonyl Compounds

“…However, organozirconate complexes, which usually have an 18‐electron configuration with two cyclopentadienyl (Cp) rings, three ZrC bonds, and alkali counter ions, have rarely been explored in spite of being the supposed intermediates in a number of stoichiometric and catalytic reactions, and able to form CC bonds through a successful 1,2‐migration of organozirconates 2–4. Our research group has an interest in the above mentioned subjects, and we have recently reported5 that by adding quinone as an oxidant to a mixture of alkynylzirconates then zirconocenendiyne compounds are afforded: these compounds can be converted into various endiynes through coupling reaction with electrophiles. These results prompted us to further study the chemistry of organozirconate complexes.…”

Zirconoarylation of alkynes through p-chloranil-promoted reductive elimination of arylzirconates

“…Recently, we have reported a p -chloranil (TCQ)-promoted reductive elimination reaction of the zirconate complex Li[Cp 2 Zr(C≡CR) 3 ] toward geminal enediynes [ 44 ]. As part of our ongoing project on organozirconate chemistry [ 45 – 48 ], we envisioned that the use of an aryl ligand instead of one of the alkynyl ligands would provide an arylzirconation product of the alkyne.…”

Coupling Reactions of Zirconate Complexes Induced by Carbonyl Compounds

“…This multiple reactivity make allenes as excellent candidates for synthetic manipulation. Chloroformates afforded the corresponding allenes in 47-61 % yields (Table 1, entries [1][2][3][4][5]. A variety of acyl compounds were subjected to this novel reaction and all reactions afforded analogous products in good to high yields after hydrolysis.…”

“…[1] However, organozirconate complexes, which usually have an 18-electron configuration with two cyclopentadienyl (Cp) rings, three Zr À C bonds, and alkali counter ions, have rarely been explored in spite of being the supposed intermediates in a number of stoichiometric and catalytic reactions, and able to form CÀC bonds through a successful 1,2-migration of organozirconates. [2][3][4] Our research group has an interest in the above mentioned subjects, and we have recently reported [5] that by adding quinone as an oxidant to a mixture of alkynylzirconates then zirconocenendiyne compounds are afforded: these compounds can be converted into various endiynes through coupling reaction with electrophiles. These results prompted us to further study the chemistry of organozirconate complexes.…”

“…The representative results are summarized in Table 1. Chloroformates afforded the corresponding allenes in 47-61 % yields ( Table 1, entries [1][2][3][4][5]. The addition of esters similarly gave allenes in good yields ( Table 1, entries [6][7][8].…”