One-Step Synthesis of Fully Functionalized Pyrazolo[3,4‑<i>b</i>]pyridines via Isobenzofuranone Ring Opening
Andrés Charris-Molina
Juan-Carlos Castillo
Mario Macías
Jaime Portilla
10.1021/acs.joc.7b02471.s001
https://acs.figshare.com/articles/journal_contribution/One-Step_Synthesis_of_Fully_Functionalized_Pyrazolo_3_4_i_b_i_pyridines_via_Isobenzofuranone_Ring_Opening/5616523
A novel series of fully substituted
pyrazolo[3,4-<i>b</i>]pyridines <b>4</b> has been
prepared in a regioselective manner
by the microwave-assisted reaction between <i>N</i>-substituted
5-aminopyrazoles <b>1</b> and 3-(3-oxo-2-benzofuran-1(3<i>H</i>)-ylidene)pentane-2,4-dione (<b>2</b>). This is the
second reported example of a cyclocondensation reaction using substrate <b>2</b> as a 1,3-bis-electrophilic reagent. Remarkably, this synthesis
offers functionalized products with acetyl and carboxyl groups in
one step, in good yields, and with short reaction times. Additionally,
the cyclization intermediate <b>3</b> was isolated, allowing
us to postulate a mechanism for this reaction, which is initiated
via isobenzofuranone ring opening of <b>2</b> in a Michael-type
reaction. The structures of the products and regioselectivity of the
reactions were determined on the basis of NMR measurements and X-ray
diffraction. For this new reaction using substrate <b>2</b>,
the optimal reaction conditions and its scope were investigated.
2017-11-10 00:00:00
substrate 2
5- aminopyrazoles 1
isobenzofuranone ring opening
NMR