ChemInform Abstract: Cyclization Reactions of Nitriles. Part 23. Addition of Active Phenols to Electron Deficient Ethenes Accompanied by Cyclization to 2‐Amino‐4H‐benzo(b)pyrans.

Abstract

The activated phenols (I) as well as 2‐naphthol (IV) react with electron‐deficient alkenes like (II) to yield the 2‐amino‐4H‐benzo(b)pyrans (III) or the 2‐amino‐4H‐naphtho‐(2,1‐b)pyrans (V).

5-Acetyl-2-amino-6-methyl-4-(3-nitrophenyl)-4H-pyran-3-carbonitrile and 2-amino-5-ethoxycarbonyl-6-methyl-4-(3-nitrophenyl)-4H-pyrano-3-carbonitrile

“…The dihedral angle between the pseudo-axial aryl substituent and the C2/C3/C5/C6 plane of the boat of the heterocycle is 84.0 (1) in (I) and 98.7 (1) in (II), minimizing possible intramolecular steric contacts in both molecules. Similar orientations of sterically demanding substituents were found in all previously determined derivatives of 4H-pyrans (Sharanina et al, 1986;Klokol et al, 1987;Shestopalov et al, 1991;Samet et al, 1996;Kislyi et al, 1999a,b;Florencio & Garcia-Blanco, 1987;Bellanato et al, 1988;Lokaj et al, 1990;Marco et al, 1993). The value of the angle is close to 90 in practically all known 4H-pyran derivatives containing sterically demanding substituents in the 4-position of the heterocycle.…”

“…Structural studies of some derivatives of 4H-pyrans by X-ray analysis have been published (Florencio & Garcia-Blanco, 1987;Bellanato et al, 1987Bellanato et al, , 1988Lokaj et al, 1990;Marco et al, 1993). The present study represents a continuation of our investigations of the structures of 4H-pyran derivatives (Sharanina et al, 1986;Klokol et al, 1987;Shestopalov et al, 1991;Samet et al, 1996;Kislyi et al, 1999a,b). The crystal structures of 5-acetyl-2-amino-6-methyl-4-(3-nitrophenyl)-4H-pyran-3-carbonitrile, (I), and 2-amino-5-ethoxycarbonyl-6-methyl-4-(3-nitrophenyl)-4H-pyrano-3-carbonitrile, (II), are presented herein.…”

“…The C6ÐC5ÐC8ÐO2 torsion angle is À179.3 (2) in (I) and À157.2 (2) in (II). It is interesting to note that the acetyl substituent has a cis geometry in the 1,4dihydropyridine derivative described by Nesterov et al (1985), and ester groups have cis geometry in substituted 4H-pyrans and form intramolecular hydrogen bonds with amino groups (Sharanina et al, 1986;Klokol et al, 1987;Shestopalov et al, 1991).…”

N—H...O and N—H...N interactions in three pyran derivatives

“…Similar orientations of sterically demanding substituents were found in all previously determined derivatives of 4H-pyrans (Sharanina et al, 1986;Klokol et al, 1987;Shestopalov et al, 1991;Samet et al, 1996;Florencio & García-Blanco, 1987;Bellanato et al, 1988;Lokaj et al, 1990;Marco et al, 1993). The value of the angle is close to 90 in practically all known 4H-pyran derivatives containing sterically demanding substituents in the 4-position of the heterocycle.…”

Reactions of carbonyl compounds with α,β-unsaturated nitriles as a convenient pathway to carbo- and heterocycles

“…This affords substituted 4H-benzo[b]pyrans 208 in 65% ± 90% yields. 142,143 On refluxing in ethanol for 15 min in the presence of piperidine, non-substituted phenol also gives pyrans 208 (R = R H = H). 144 Under similar conditions, 2-naphthol 209 reacts with the nitriles 42 and 59 to give substituted 4H-naphtho[2,1-b]pyrans 210.…”