Thianaphthen-2-one chemistry. I. Synthesis of 6H-benzothieno[3,2-c][1]benzopyran-6-ones (11-thiacoumestans)

Abstract

The condensation of thianaphthen-2-one and salicylaldehyde gave 6a,lla-dihydro-6H-benzothieno [3,2c] [l]benzopyran-6-one (dihydro-11 -thiacoumestan). Several analogs were prepared. Oxidation of the dihydro compounds with DDQ (2,3-dichloro-5,6-dicyano-l,4-quinone) gave 6H-benzothieno[3,2-c][l]benzopyran-6-ones (11-thiacoumestans), a new heterocyclic ring system, and the sulfur analog of the naturally occurring 6H-benzofuro[3,2-c][l]benzopyran-6-one (coumestan) ring system. The reaction of thianaphthen-2-one with 5-nitrosalicylaldehyde and pyridoxal in alcohol gave the corresponding 2-aryl-2,3-dihydrothianaphthene-3-carboxylates.

Palladium‐Catalyzed Synthesis of Benzothiophenes via Cross‐Dehydrogenative Coupling of 4‐Arylthiocoumarins and Pyrones

“…We proposed that widely available coumarin would act as a template for the direct synthesis of benzothiophenes by cross‐dehydrogenative coupling (CDC) (Scheme ) . In particular, accessing benzothieno[2,3]coumarins has proven challenging; the classic methods involve directed ortho‐metallation reported by Snieckus and carbonylative cross‐coupling using an acetoxy group as the nucleophile reported by Larock (Scheme A–B). However, both methods build‐up on an existing benzothiopene ring, and are limited in terms of atom‐ and step‐economy.…”

An Efficient Synthesis of Coumestrol and Coumestans by Iodocyclization and Pd‐Catalyzed Intramolecular Lactonization.

“…The resulting mixture was then extracted with Et 2 O, washed successively with water and satd aq NaCl, dried over anhydrous Na 2 SO 4 , and concentrated under vacuum. The residue was purified by flash chromatography on silica gel (1:1 hexane/ EtOAc) to afford compound 7 as a colorless oil: 1 (9). This compound was prepared according to a literature procedure 6 and was obtained as a yellow solid: mp 98-100 °C; S5 1 H NMR (CDCl 3 ) δ 1.78 (s, 3H), 7.23-7.27 (m, 1H), 7.36 (dd, J = 0.9, 8.…”

“…The spectral properties were identical to those previously reported. 9 11-Methylbenzopyrano [4,3-b]indol-6-one (6). This compound was obtained as a light yellow solid (75%): mp 251-252 ºC (lit.…”

Synthesis and Pharmacology of Conformationally Restricted Raloxifene Analogues: Highly Potent Selective Estrogen Receptor Modulators

“…22 Thiacoumestans 6a-c were prepared by the condensation of a salicyl aldehyde with thianaphthen-2-ones 10a,b followed by oxidation, demethylation, and silylation (Scheme 1a). 23 This protecting group interchange was necessary, both for ease of removal and to provide improved solubility in later stages of the synthesis (vide supra). Compounds 10a,b were in turn prepared either by hydrolysis of the 2-(dimethylamino)benzothiophene, 8, 24,25 or from benzothiophene via oxidation of the corresponding boronic acid, 9.…”