ChemInform Abstract: SYNTHESIS AND DEHYDROBROMINATION OF 2,2,2‐TRIBROMO‐1‐ARYLETHANES

Abstract

Das aus Bromoform freigesetzte Tribrommethylanion reagiert mit den Arylbrommethanen (I) zu den Tribrommethylarylmethanen (II), die je nach Wahl der Reaktionsbedingungen in die Dibromalkene (III) oder die Monobromalkine (IV) übergeführt werden.

3α-Hydroxy-3β-(phenylethynyl)-5β-pregnan-20-ones: Synthesis and Pharmacological Activity of Neuroactive Steroids with High Affinity for GABAA Receptors

“…The activity of these 3β-(phenylethynyl) compounds in the TBPS binding assay was found to be highly dependent on the substitution on the phenyl ring. Substitution with an electron-withdrawing group at the 4-position of phenyl ring increased the affinity, e.g., 4-CN (13 11 800 nM, predominant low-affinity component). Although, the 4-OH substitution decreased the activity, a gradual increase in activity was observed in moving the hydroxy group closer to the steroid nucleus.…”

“…General Method for the Preparation of 2,2-Dibromophenylethene Derivatives (9). To a well-stirred solution of CBr 4 (2.985 g, 9 mmol) in CH 2 Cl 2 (20 mL) at 0 °C were added PPh 3 (4.75 g, 18.1 mmol) and then the benzaldehyde derivative ( 8 , 9 mmol). Stirring was continued at 0 °C for 20 min, at which point water (20 mL) was added.…”

“…The synthesis of 3β-substituted phenylethynyl derivatives is depicted in Scheme . The Wittig reaction of the corresponding benzaldehyde ( 8 ) with carbon tetrabromide in the presence of 2 equiv of triphenylphosphine afforded the intermediate phenyldibromoethene ( 9 ) …”

“…The Wittig reaction of the corresponding benzaldehyde (8) with carbon tetrabromide in the presence of 2 equiv of triphenylphosphine afforded the intermediate phenyldibromoethene (9). 13 The dibromoethene derivative was then allowed to react with 2 equiv of n-butyllithium to generate, in situ, lithium phenyl acetylide, which was then reacted with the ketone 2 to give, after hydrolysis of the 20-ketal, the corresponding phenylethynyl derivatives (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20).…”

A Novel Synthesis of β,β-Dibromostyrenes

“…The known compounds 2a, 2f, 2i were identified by comparison of their spectral data with those described in the literature. 22 Arylbromoacetylenes; General Procedure A solution of the hydrazone (10 mmol) in DMSO (10 mL) was treated as described for the dibromostyrenes. After 4 h, a solution of DBU (4.5 mL, 30 mmol) in DMSO (20 mL) was added dropwise over 10 min, maintaining the temperature at 20°C.…”