ChemInform Abstract: A Diastereoselective Cobalt-Mediated Synthesis of Benzopyrans Using a Novel Variation of an Intramolecular Nicholas Reaction in the Key Cyclization Step: Optimization and Biological Evaluation.

✍ Scribed by A. MANN; C. MULLER; E. TYRRELL

• Publisher: John Wiley and Sons
• Year: 2010
• Weight: 42 KB
• Volume: 29
• Category: Article
• ISSN: 0931-7597
• DOI: 10.1002/chin.199836177

✦ Synopsis

A Diastereoselective Cobalt-Mediated Synthesis of Benzopyrans Using a Novel Variation of an Intramolecular Nicholas Reaction in the Key Cyclization Step: Optimization and Biological Evaluation.

-A variation of the Nicholas reaction between a hexacarbonyldicobalt-stabilized cation and a trisubstituted alkene in a one-pot procedure is undertaken to afford novel benzopyrans such as (X) and (XIII). The synthesis of the cyclization precursors (XII) is conducted by an O-alkylation followed by the propynylation step. Reversal of these steps leads to a significant reduction in the yield. The Lewis acid serves two functions (i) in the generation of the cobalt stabilized propynylic cation and (ii) as a source of halogen. Several other Lewis acids [cf. (XIV)] effect the cyclization reaction. The biological activities of (X) and (XIII) are compared with the activity of the antihypertensive agent cromakalim 2. -