Selective cyclization of alkynols and alkynylamines catalyzed by potassium tert-butoxide

Alkali‐Metal Promoted Chemo‐ and Regioselective Cycloisomerization Reactions to (Z)‐3‐Alkylideneisoindolin‐1‐ones: Unusual Positive Role of H2O

“…Based on the above mentioned results and the previous alkali metal ions‐promoted intramolecular cyclization of 2‐ethynylarenes,, we proposed a possible mechanism for this Na 2 CO 3 /H 2 O‐mediated anionic heterocyclization reaction (Scheme ). While strong bases such as NaH or t BuOK have been used to induce a similar cycloisomerization,, reports on the usage of a mild base to promote deprotonation of enamides to form cyclic azaheterocycles have been proven to be effective . Therefore, the nitrogen anionic species A can be proposed.…”

“…Early in 1995, Weingarten and Padwa reported stoichiometric NaH‐induced exo ‐cyclization reaction of electron‐varied o ‐ethynylaryl benzylic alcohols . An improved reaction was disclosed by Liu et al , who developed t BuOK‐catalyzed selective cycloisomerization of alkynols or alkynylamines, to selectively produce exo ‐alkenyl heterocyclic products . Most recently, Gabriele and co‐workers reported a selective synthesis of ( Z )‐3‐alkylideneisoindolinone diastereoisomers through CuCl 2 ‐catalyzed cyclization reaction of 2‐alkynylbenzamides in ionic liquids (1‐ethyl‐3‐methylimidazolium ethyl sulfate, EmimEtSO 4 ) …”

Synthesis of Substituted 1‐Alkylidenephthalanes via Lithium‐Promoted 5‐exo‐dig Cyclization

“…[24] Patil et al demonstrated with their synthesis of 1-(2alkoxyvinylidne)-2-benzopyrans the general stability of the 1,3dialkoxyallene structure. [12,14,[26][27][28] In order to support the calculated reaction mechanism, various experiments were conducted. This transformation was used for the synthesis of various furans.…”

Hydrazone–Cu‐Catalyzed Suzuki–Miyaura‐Type Reactions of Dibromoalkenes with Arylboronic Acids

“…In the case of the reaction of 1‐(2,2‐dibromovinyl)‐4‐methoxybenzene ( 1a ) with 2‐hydroxyphenylboronic acid ( 2j ), the internal alkyne product 2‐[(4‐methoxyphenyl)ethynyl]phenol was not detected. Instead, we obtained a 10 % yield of 2‐(4‐methoxyphenyl)benzofuran, which was formed by annulation of the internal alkyne product in the presence of a large amount of base (entry 17). The reaction of 1‐(2,2‐dibromovinyl)‐2‐(methoxymethoxy)benzene ( 1i ) with 2‐bromophenylboronic acid ( 2k ) did not give the coupling product but gave bromoalkyne derivative 1i′ in 63 % yield (entry 18).…”

“…2‐(4‐Methoxyphenyl)benzofuran: (Table , entry 17). 2‐(4‐Methoxyphenyl)benzofuran was obtained from 1‐(2,2‐dibromovinyl)‐4‐methoxybenzene ( 1a ; 72.2 mg) and 2‐hydroxyphenylboronic acid ( 2j ; 69.4 mg) according to the general procedure in 10 % yield (14.5 mg, 0.0254 mmol) as a white solid.…”