Synthesis of propargylic ethers via Lewis-acid mediated nucleophilic substitution of propargylic esters

Scope and advances in the catalytic propargylic substitution reaction

“…TiCl 4 has been utilized as an efficient Lewis acid catalyst by Mahrwaid and co-workers in the year 1999 for the direct displacement of propargylic esters 71 with diverse oxygencentered nucleophiles, Scheme 30. 62 Alcoholic solvents like MeOH, EtOH, i PrOH, t BuOH resulted in decreased product yield with concomitant formation of hydrolyzed products. Even with aliphatic substituents hydrolyzed products were mainly obtained probably due to the decreasing stabilization of the formed cation during the reaction.…”

“…TiCl 4 has been utilized as an efficient Lewis acid catalyst by Mahrwaid and co-workers in the year 1999 for the direct displacement of propargylic esters 71 with diverse oxygen-centered nucleophiles, Scheme 30 . 62 …”

Lewis Acid-Catalyzed Propargylic Etherification and Sulfanylation from Alcohols in MeNO2-H2O

“…In contrast, 2°alcohols such as cyclopentanol and cyclohexanol afforded 2ad and 2ae (entries 3 and 4). Surprisingly, both 1°and 2°alcohols are also nucleophilic toward propargyl cations in MeNO 2 -H 2 O. Alcohols bearing other aromatic substituents at the R 1 -position were examined with the 1°and 2°alcohols (entries [6][7][8][9][10][11][12][13][14][15][16][17]. Alcohol 1d, bearing the bulky aromatic substituent, 2,4,6-trimethylphenyl, also produced propargylic ether 2da in excellent yield (entry 12).…”

“…However, substitution of hydroxyl group in an alcohol generally requires the prior activation of the hydroxyl group because of the poor leaving ability of this group. 5,6) An alcohol used as a precursor for carbocations is usually activated by transforming it to the corresponding acetate, [7][8][9][10][11][12][13][14][15][16][17] carbonate, 18,19) halide, 20) phosphonate. 21,22) Prior activation of an alcohol is also necessary if it has to be used as a nucleophile because of its low nucleophilicity.…”

Synthetic Applications of Azolium Ylides to a Traceless Solid-Phase Synthesis of 2-Substituted Azoles

“…Increasing the equivalents of TFA to equal piperidine or even to excess gave only a trace of the cleavage product. Lewis acids are known to mediate the solvolysis reactions of propargylic esters . We examined the use of Lewis acids as an additive and found that addition of boron trifluoride etherate to the reaction media (method B) significantly improved the yield of the solvolysis reactions .…”