Synthesis of Dihydro‐5H‐Benzo[c]‐Fluorenes, Dihydroindeno[c]‐Chromenes and Thiochromenes via Intramolecular Cyclization and their Effect on Human Leukemia Cells

Abstract

In this work, we describe the construction of a series of 6,7-dihydro-5Hbenzo[c]fluorenes. Their synthesis is based on an intramolecular-cyclization of tricyclic substrates, which has an alcohol functional group in acidic conditions at ambient temperature. Certain reaction optimization conditions reveal that triflic acid was the most convenient reagent for this transformation, affording a broad range of fluorene derivatives in a 37 to 93% yield. We illustrate the robustness of this methodology through a gram-scale synthesis, and the preparation of dihydroindeno[c]-chromenes thiochromenes, and azulenes derivatives.

Leveraging in situ N-tosylhydrazones as diazo surrogates for efficient access to pyrazolo-[1,5-c]quinazolinone derivatives

“…23 Nagendra Babu et al used a domino reaction with 3-ylideneoxindoles and diazo partners, leading to pyrazoloquinazolinones (Scheme 1f ). 24 Given our sustained interest in studying the reactivity of N-tosylhydrazones (NTHs), [25][26][27][28][29][30][31][32] we formulated plans to investigate reactions involving these reactive species for the construction of N-heterocyclic moieties, specifically the pyrazolo-[1,5-c] quinazolinone scaffold. Within this framework, we conceived an original strategy for pyrazolo-[1,5-c]quinazolinone synthesis through intramolecular cycloaddition (Scheme 1g).…”