LiOtBu-Promoted Intramolecular 1,3-Dipolar Cycloaddition of the 2'-Alkynyl-biaryl-2-aldehyde N-Tosylhydrazones
Jiaying Lv1, Ruimao Hua1,2
1Key Laboratory of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, China.
Abstract:
A two-step, one-pot synthesis of 3-substituted 1H-dibenzo[e,g]indazoles in good to high yields via a LiOtBu-promoted intramolecular 1,3-dipolar cyclization of 2'-alkynyl-biaryl-2-aldehyde N-tosylhydrazones was developed. The N-Ts-hydrazones used were prepared in situ via the reactions of 2'-alkynyl-biaryl-2-aldehydes and TsNHNH2(p-methylbenzenesulfonohydrazide). Two types of signals related to the hydrogen bonds, forming in several products, were observed in the 1H NMR spectra recorded in DMSO-d6, assigned to N-H bonds in their dimeric species of product and tautomer.
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