42216-96-6Relevant articles and documents
Synthesis of Substituted 1-Alkylidenephthalanes via Lithium-Promoted 5-exo-dig Cyclization
Bunse, Paul,Würthwein, Ernst-Ulrich,Wünsch, Bernhard
supporting information, p. 1806 - 1812 (2018/04/27)
A one-pot synthesis of 1-alkylidenephthalanes from 3-(2-bromophenyl)propyne derivatives has been developed. 3-(2-Bromophenyl)propynal acetals 9 and corresponding orthoester 19 were treated successively with n-butyllithium and various aldehydes and ketones at low temperature to obtain 1-alkylidenephthalanes 10 and 20 with various functional groups at the exocyclic methylene moiety. Halogen-metal exchange, nucleophilic addition to various carbonyl compounds, regioselective 5-exo-dig cyclization of the respective intermediate lithium alcoholate and hydrolysis represent the key steps in this Domino reaction. A two-step mechanism involving at first a synchronous cyclization to form a vinyllithium intermediate and then a methoxide elimination leading to the respective 1-methoxy allenes is suggested based on DFT-calculations.
Ethynyl Ortho Esters as Precursors of Propargyl Cations. The Low-Temperature, Ionic Diels-Alder Addition of Ethyl Propiolate to 1,3-Dienes via Ethynyl Ortho Esters
Gassman, Paul G.,Chavan, Subhash P.
, p. 3407 - 3410 (2007/10/02)
3,3,3-Triethoxypropyne (triethyl orthopropiolate) was added to a series of 1,3-dienes at low temperature in the presence of trimethylsilyl triflate to yield the 4? + 2? products of the formal addition of ethyl propiolate to the 1,3-dienes.