Ether formation mesylate

The almost instantaneous intramolecular ether formation by reaction of phenoxy anions, generated from the silyl ethers with a stoichiometric amount of tetra-n-butylammonium fluoride, on mesylate esters has been used to synthesize labile benzo-0-2-isocephams (>90%) [20]. 

A pentacyclic diterpene 1 called dictyoxetane contains a most unusual subunit, a 2,7-dioxatricyclo[4.2.1.03>8 ]nonane. During model studies designed to provide access to this key subunit the bicyclic ether 2 was synthesised in the hope that Sn displacement would generate the unsaturated tricyclic oxetane. There was no reaction when 2 was treated with base. Reaction with a catalytic amount of p-toluenesulfonic acid in DMF at 75°C for 24 hours resulted only in formation of 4-methylacetophenone. The hydroxy mesylate 2 is also reported to decompose to 4-methylacetophenone on storage. 

Alternatively, diltiazem (30) has been prepared using the Evans auxiliary derivative 31 derived from L-valine (Scheme 23.7).55 After dehydration of the adduct from the condensation of 31 with anisaldehyde through the mesylate, the enol ether was formed with a Z E ratio of 4 1. This imide was then treated with 2-aminothiophenol in the presence of 0.1 equiv. 2-aminothiophenoxide with no change in the isomer ratio. The auxiliary was removed with trimethylaluminum, with concomitant formation of the lactam. After separation by crystallization, the correct diastereoisomer was converted to diltiazem in >99%ee. 

The formation of these charged complexes in solution has been used as the basis for an electrophoretic separation of the Schardinger dextrins. Beckmann and Forster also found that complex formation with a-dextrin enhances approximately 2J- -fold the ultraviolet absorption maxima in iodine-iodide solutions at 290 and 350 m/i. It is probable that the colored complexes of iodine with methyl ethers and with the tosyl and mesyl esters of the Schardinger dextrins are also inclusion compounds of the same general type. 

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