Preparation of enol ether

All of the glassware used in the preparation of enol ether (3) was dried for at least 10 min at 200°C, assembled hot, and allowed to cool under an atmosphere of argon. 

Preparation of enamines, 409 Preparation of enol acetates, 411 Preparation of enol ethers, 409 Preparation of a-halo ketones, 267 Preparation of 3/3-hydroxyandrosta-5,15-dien-17-one, 302... 

Enol and enolate reactions at oxygen preparation of enol ethers... 

Preparation of enol ethers. Condensation of a 3-keto-5o -steroid (1) with triethyl orthoformate in ethanol containing a trace of hydrogen chloride affords the diethyl ketal (2) in good yield when refluxed in xylene the ketal loses a molecule of ethanol and affords the A -enol ether (3). A A -3-ketosteroid (4) when condensed with... 

Alkylation of enolate anions usually gives C-alkylation and is therefore not suitable for the preparation of enol ethers. The exception is when triethyloxonium tetrafluoroborate is used as the alkylating agent in a dipolar aprotic solvent. 0-Alkylation can be regioselectiveiy achieved if the enolate anion is derived from acetoacetate or a similar compound. On the other hand, 0-acylation of enols or enolate anions is quite common. Enol esters can therefore be prepared readily from the parent carbonyl compounds. For... 

Hydroalkoxylation of alkynes, or the addition of alcohol to alkynes, is a fundamental reaction in organic chemistry that allows the preparation of enol ethers and a variety of oxygen-containing heterocycles such as furan, pyran, and benzofuran derivatives. Bergbreiter et al. found that a Mnear poly-(A-isopropylacrylamide) (PNIPAM) polymer exhibited inverse temperature solubility in water (i.e., soluble in cold water but insoluble in hot water). A recoverable homogeneous palladium catalyst was prepared based on the polymer. The PNIPAM-bound Pd(0) catalyst was effective for the reaction of 2-iodophenol with phenylacetylene in aqueous THE media to give the target product... 

ENOL AND ENOLATE REACTIONS AT OXYGEN PREPARATION OF ENOL ETHERS... 

A mixture of cis- and truns-1-methoxycyclododecenes was prepared in 98% yield from cyclododecanone by a modification of Claison s method of ketal formation. Amberlyst-15 is a superior catalyst for the preparation of enol ethers and acetals. 

E-Alkenylpentafluorosilicates [e.g. (31)], which are readily obtained from acetylenes by hydrosilylation, are useful intermediates for the preparation of -enol ethers (32)" and thiocyanates (33). Both processes are compatible with cyano and ester groups, and when terminal silicates are used stereoselectivity is very high (>99%). Primary alcohols give the highest yields of enol ethers, whereas tertiary alcohols do not react, and allylic alcohols give the particularly useful allyl vinyl ethers. 

Scheme 4.44. Preparation of enol ethers and alkenyl sulfides by the use of a-heteroatom-substituted carbene complexes...

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