Reaction of Indazole with Terminal Di‐bromoalkanes and Their Subsequent Thermal Cyclization: A Facile Entry into Fused Indazole Ring Systems

Abstract

1‐(ω‐Bromoalkyl)indazoles undergo a facile thermal intramolecular cyclization reaction in the neat form. The reactions do not require the use of a solvent or base and proceed in quantitative yields. Moreover, their corresponding 2‐substituted isomers also cyclize affording the same cycloadducts. These reactions provide a facile entry into the synthesis of fused indazole ring systems with potential medicinal properties.

Keywords:

• Di‐bromoalkanes
• G‐protein coupled receptors
• indazole
• intramolecular cyclization

Acknowledgment

The authors thank Leon Zhou for HRMS analysis.

Notes

¹See drug databases like IDDB3 for such drugs. Examples are granisetron for Emesis and Lonidamine for cancer. For Lonidamine (see the following reference:[3]).

²Such examples are extensive, mainly the indole alkaloids family of strychnine, brucine, eburnamonine, etc.