Ni-Catalyzed Highly Regio- and Chemoselective Cocycloaddition of Nonconjugated Diynes with 1,3-Diynes:  A Novel Method for Polysubstituted Arylalkynes

Abstract

[reaction: see text] Effective nickel-catalyzed cocycloaddition of nonconjugated diynes with conjugated diynes yields polysubstituted arylalkynes in good to excellent yields with high regio- and chemoselectivity.

[2+2+2] Cocyclotrimerization with Ferrocenylalkynes

“…There are only three reports of catalytic homocyclotrimerization of ferrocenylethyne and so we undertook a systematic investigation of the catalytic activity of transition metal complexes that could be expected to induce a smooth cocyclotrimerization of ferrocenylalkynes with diynes. Thus, we decided to assess the activity of [RhCl(PPh 3 ) 3 ], [9] [NiL 2 Br 2 ]/Zn (L 2 ϭ 2PPh 3 , [10] dppe [11] ), [{IrCl(cod)} 2 ]/dppe, [12] [CpCo(cod)]/ 2PPh 3 , [5g] and [CoBr(PPh 3 ) 3 ] [13] as the catalyst precursors for the cocyclotrimerization of ferrocenylethyne (1a) with dipropargyl malonate (2a) to 3aa (Scheme 2). The results are summarised in Table 1. [2ϩ2ϩ2] Cocyclotrimerization with Ferrocenylalkynes FULL PAPER The best yields were obtained with Rh-and Co-based catalysts.…”

Construction of Substituted Benzene Rings by Palladium‐Catalyzed Direct Cross‐Coupling of Olefins: A Rapid Synthetic Route to 1,4‐Naphthoquinone and Its Derivatives

“…N-phenylmaleimide (1 g) could serve as an electron-deficient olefin in the crosscoupling reaction with 2 d, although 3 v was produced in much lower yield [Eq. (2)]. Our attempts to improve the yields of these reactions failed at this stage.…”

“…An alternative approach to polysubstituted benzene rings is the transitionmetal-catalyzed [2+2+2] cyclotrimerization of alkynes. [2] This route has the advantage of the rapid construction of highly functionalized molecular frameworks in one step compared with electrophilic aromatic substitution reactions (Scheme 1 a). By using this strategy, intermolecular reactions provide a versatile tool for the ring synthesis of complex molecular products.…”

Cycloaddition of 1,3-Butadiynes: Efficient Synthesis of Carbo- and Heterocycles

“…In the presence of NiBr 2 and zinc powder, the chemo- and regioselectively controlled [2+2+2] cycloaddition of nonconjugated diynes with 1,3-butadiynes at 80 °C in CH 3 CN afforded the potential alkynyl benzene synthetic intermediates in 53%–88% yields. (Scheme 4) [25].…”