The oxidative annulation of tertiary benzyl alcohols with internal alkynes using an (electron-deficient η5-cyclopenta-dienyl)rhodium(III) catalyst under ambient conditions
It has been established that a dinuclear (electron-deficient η5-cyclopentadienyl)rhodium(III) complex catalyzes the oxidative annulation of tertiary benzyl alcohols with internal alkynes via sp2 C-H/O-H functionalization under ambient conditions (at room temperature under air) to give substituted isochromenes in good yields. The preference for annulation across electron-rich substrates over electron-deficient substrates was observed using this electron-deficient rhodium(III) complex.
Fukui, Miho,Hoshino, Yuki,Satoh, Tetsuya,Miura, Masahiro,Tanaka, Ken
p. 1638 - 1644
(2014/06/09)
Ruthenium(II)-catalyzed synthesis of isochromenes by C-H activation with weakly coordinating aliphatic hydroxyl groups
Cationic ruthenium(II) complexes have been employed for the highly effective oxidative annulation of alkynes with benzyl alcohols to deliver diversely decorated isochromenes. The hydroxyl-directed C-H/O-H functionalization process proceeded efficiently under an atmosphere of air. Detailed mechanistic studies were indicative of a kinetically relevant C-H metalation. Cationic ruthenium(II) complexes enabled highly efficient oxidative annulation of alkynes with benzylic alcohols to deliver isochromenes (see scheme). This aliphatic hydroxyl-directed C-H/O-H activation proceeded efficiently under an air atmosphere. Mechanistic studies were indicative of an irreversible C-H metalation as the rate-limiting step.
Nakanowatari, Sachiyo,Ackermann, Lutz
supporting information
p. 5409 - 5413
(2014/05/20)
Synthesis of isochromene and related derivatives by rhodium-catalyzed oxidative coupling of benzyl and allyl alcohols with alkynes
The straightforward synthesis of isochromene derivatives and related cyclic ethers is achieved by the rhodium-catalyzed oxidative coupling of α,α-disubstituted benzyl and allyl alcohols with alkynes. The hydroxy groups effectively act as the key function for the regioselective C-H bond cleavage.