Nickel-catalyzed cocyclotrimerization of oxa- and azabenzonorbornadienes with alkynes: reaction with multiple synthetic applications

Recent Advances in the Transition-Metal-Catalyzed Regioselective Approaches to Polysubstituted Benzene Derivatives

“…High regioselectivity has been observed in many examples. Similar reactions were also reported by Cheng et al28a The nickel−zinc catalytic system was also used in the cocyclotrimerization of oxa- and azabenzonorbornadienes with alkynes 28b …”

Nickel-Catalyzed Highly Regio- and Stereoselective Cyclization of Oxanorbornenes with Alkyl Propiolates: A Novel Method for the Synthesis of Benzocoumarin Derivatives

“…Transition metal catalyzed cyclizations of alkenes and alkynes are powerful methods for the synthesis of various carbocyclic and heterocyclic compounds 1. Recently, we2, 3 and others4, 5 observed that nickel complexes effectively catalyze the cycloaddition of 7‐oxa‐ and 7‐azabenzonorbornadienes with alkynes to give [2+2]2 and [2+2+2]3a,3b cycloadducts (Scheme ). The reactions of alkenes with alkynes depend greatly on the reaction conditions.…”

“…Other bidentate phosphines such as 1,1′‐bis(diphenylphosphanyl)ferrocene (dppf), methylenebis(diphenylphosphane) (dppm), and 1,3‐propanediylbis(diphenylphosphane) (dppp) are less effective, giving 3 a in 53, 47, and 26 % yield, respectively. Nickel complexes of monodentate phosphines that are efficient catalysts for the [2+2]2 and [2+2+2]3a,3b cycloaddition of 1 a with various alkynes are essentially inactive in the formation of 3 a .…”

Lewis Base‐Catalyzed Cycloaddition of Heterocyclic Alkenes with 2,2,2‐Trifluorodiazoethane (CF3CHN2): Access to Trifluoromethylated Pyrazolines and Pyrazoles

“…Due to the angle strain and the proximal heteroatom coordination, heterobicyclic alkenes are versatile synthetic building‐blocks for the construction of complex cyclic frame works in various types of organic transformations including metal‐catalyzed cycloaddition reactions, [10a–g] metal‐catalyzed C−H addition and annulations, [10h–j] ring opening reactions [10k–l] . Oxa ‐ and aza‐ bicyclic alkenes, such as oxa ‐ and aza ‐benzonorbornadienes, have been recognized as useful building blocks in molecular architecture as they can serve as general templates to create highly substituted ring systems [11] .…”