Potassium 1,1,3,3-Tetracyano-2-[2-(methoxycarbonyl)benzoyl]prop-2-enide in the Synthesis of Spiro-Fused Isobenzofuran De
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Potassium 1,1,3,3-Tetracyano-2-[2-(methoxycarbonyl)benzoyl]prop-2-enide in the Synthesis of Spiro-Fused Isobenzofuran Derivatives Ya. S. Kayukova,*, S. V. Karpova, A. A. Grigorʼeva, and O. V. Kayukovab,** a
I.N. Ulʼyanov Chuvash State University, Cheboksary, 428015 Russia b
Chuvash State Agricultural Academy, Cheboksary, 428003 Russia e-mail: *[email protected]; **[email protected] Received July 23, 2020; revised July 29, 2020; accepted August 2, 2020
Abstract—Successive treatment of potassium 1,1,3,3-tetracyano-2-(2-(methoxycarbonyl)benzoyl)prop-2-enide with concentrated sulfuric acid and water gave 2-(5′-amino-4′-cyano-3-oxo-3H,3′H-spiro[[2]benzofuran-1,2′furan]-3′-ylidene)propanedinitrile. The reaction of the title compound with sodium hydroxide, followed by neutralization with sulfuric acid afforded 4′-amino-3,3′,6′-trioxo-2′,3′,5′,6′-tetrahydro-3H-spiro[[2]benzofuran1,1′-pyrrolo[3,4-c]pyridine]-7′-carbonitrile. Keywords: tetracyanopropenide, heterocyclization, isobenzofuran, spirocyclic compounds, pyrrolo[3,4-c]pyridines
DOI: 10.1134/S1070428020100322 Spiro-fused O,N-heterocycles occur in nature and exhibit a broad spectrum of biological activity which is largely determined by their rigid three-dimensional structure [1–11]. Therefore, these compounds attract persistent interest. In particular, a spiro-fused isobenzofuran fragment is present in molecules of natural compounds such as the alkaloid lycoplanine A (calcium channel inhibitor) [12] and elmenol H (bacterial growth inhibitor) [13]. Synthetic 3H,3′H-spiro[[1]benzofuran-2,1′-[2]benzofuran]-3,3′-diones are active against influenza B viruses [14]. Modern synthetic approaches to spiro-fused isobenzofuran derivatives utilize difunctional ketones [2] and diarylacetylenes [15]. Herein, we propose to obtain spiro-fused isobenzofuran derivatives from potassium 1,1,3,3-tetracyano-2-(2-methoxycarbonyl)benzoylprop-2-enide (2) which can be prepared from 1′,3′-dioxo-1′,3′-dihydrospiro[cyclopropane-1,2′indene]-2,2,3,3-tetracarbonitrile (1) (Scheme 1) [16]. Heterocyclizations involving carbonyl and cyano groups are often used to build up various heterocyclic systems [17], and the additional electrophilic reaction center in the phenyl substituent could give rise to spiro cyclization via furan ring closure. Our studies have shown that the reaction of propenide 2 with sodium hydroxide, followed by neutraliza-
tion with dilute sulfuric acid, yields 4′-amino-3,3′,6′trioxo-2′,3′,5′,6′-tetrahydro-3H-spiro[[2]benzofuran1,1′-pyrrolo[3,4-c]pyridine]-7′-carbonitrile (3). When potassium salt 2 was initially treated with concentrated sulfuric acid and then with water, the product was 2-(5′-amino-4′-cyano-3-oxo-3H,3′H-spiro[[2]benzofuran-1,2′-furan]-3′-ylidene)propanedinitrile (4). The structure of compounds 3 and 4 was determined on the basis of their IR, 1H and 13C NMR, and mass spectra. A plausible scheme for these transformations includes intermediate formation of pyrrolo[3,4-c]pyridine and furan derivatives in which the hydroxy group is located near the
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