Synthesis of 2-trifluoromethylpyrazolo[5,1-a]isoquinolines via silver triflate-catalyzed or electrophile-mediated one-pot tandem reaction

• Xiaoli Zhou,
• Meiling Liu,
• Puying Luo,
• Yingjun Lai,
• Tangtao Yang and
• Qiuping Ding

Beilstein J. Org. Chem. 2014, 10, 2286–2292, doi:10.3762/bjoc.10.238

• electrophile-mediated conditions is described. Various trifluoromethylated pyrazolo[5,1-a]isoquinolines were afforded in moderate to excellent yield by this developed method. Keywords: [3 + 2] cycloaddition; electrophile; N’-(2-alkynylbenzylidene)hydrazide; silver triflate; tandem; Introduction Isoquinolines

• substituents are suitable partners in this process and the corresponding pyrazolo[5,1-a]isoquinolines 3e–h were obtained in good yields. Fortunately, alkyl-substituted N’-(2-alkynylbenzylidene)hydrazide was demonstrated to be good partner in the transformation. For instance, N’-(2-alkynylbenzylidene)hydrazide

• -withdrawing substituents. For instance, methyl-substituted N’-(2-alkynylbenzylidene)hydrazide 1b reacted with iodine and ethyl 4,4,4-trifluorobut-2-ynoate (2) in the presence of CsF and 4 Å MS leading to the desired product 4b in 90% yield (Table 3, entry 3). A relatively lower yield was obtained when nitro

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• carbene. (Scheme 24) [67]. As mentioned above, N’-(2-alkynylbenzylidene)hydrazide 42 could easily be transformed to isoquinolinium-2-ylamide 43 by a 6-endo-cyclization in the presence of silver triflate catalyst. Meanwhile, the in situ formed homoenolate 45 (derived from α,β-unsaturated aldehydes 44 in