Ruthenium-catalysed synthesis of o-phthalates by highly chemoselective intermolecular [2 + 2 + 2] cycloaddition of terminal alkynes and dimethyl acetylenedicarboxylate

Ruthenium-catalyzed [2 + 2+ 2] cycloaddition of three different alkynes

“…(1)) [16]. In the course of our further investigations, we found the same catalyst system could be applied to the threecomponent reaction and successfully achieved the chemoselective [2 + 2 + 2] cycloaddition of three different alkynes, by controlling the molar ratio of the substrates.…”

Ruthenium-Catalyzed Cycloadditions to Form Five-, Six-, and Seven-Membered Rings

“… Independent computational studies by Kirchner , and Saá on the mechanism of the parent Cp-ruthenium­(II)-catalyzed alkyne [2+2+2] cyclotrimerization corroborated the proposed oxidative coupling–alkyne insertion pathway. Cp*RuCl­(cod)-catalyzed crossed [2+2+2] cycloadditions of DMAD were studied further by Mitsudo, , Teplý, and Kotha, but low isomer selectivities were observed (not shown). A stunning application of Yamamoto’s crossed [2+2+2] cycloaddition of propargyl alcohols, alkynylboronate and terminal alkynes is found in Cramer’s total synthesis of the highly complex glycosylated paracyclophane natural product fijiolide A, which was reported in 2015 (Scheme ).…”

Utility of Acetylenedicarboxylate in Organic Synthesis

“…Dimethyl 3,5‐di‐n‐alkyl‐o‐phthalates 37a , 37b , 37c , 37d and dimethyl 3,6‐di‐n‐alkyl‐o‐phthalates 38a , 38b , 38c , 38d were synthesized via interaction between (DMAD, 1a ) and n‐alkynes 36a , 36b , 36c , 36d in the presence of catalyst such as Cp*RuCl(cod) (Cp* = pentamethylcyclopentadienyl, cod: 1,5‐cyclooctadiene, Ru = ruthenium) and in different solvent via [2 + 2 + 2]cycloaddition (Scheme ) .…”

“…First, the terminal alkyne 36 and DMAD ( 1a ) coordinated to an unsaturated ruthenium center ([Ru] = CP*RuCl) to form 39 , and subsequent oxidative cyclization give rutheniumcyclopentadienes 40 and 41 . The reaction with another molecule of 36 gave the intermediates 42 and 43 , which with loss [Ru] agine to give the products 37 and 38 .…”