Propargylic alcohols thermal rearrangement

A mercury-free route to allyl vinyl ethers that relies on the Michael addition of allyl alcohols to unsubstituted alkenyl sulfoxides, followed by thermal loss of sulfenic acid and concurrent Claisen rearrangement has been described [145]. This methodology has been applied to the synthesis of isocar-bacyclin [146]. Posner reported an acid-catalyzed protocol that produces conjugated dienoate esters from allylic alcohols and a sulfinyl orthoester [147]. Additionally, the use of propargyl alcoholates and a chloro alkenyl sulfox-... 

Thermal rearrangement of imidate esters of propargylic alcohols leads via N-acylaminoallenes to N-acyl-1-amino-1,3-dienes or /V-acyl-2-amino-1,3-dienes, depending upon the substitution of the propargylic alcohol (Scheme 27). ... 

When simple aldehydes were converted to allylic alcohols, they could be transformed to the corresponding trichloroacetimidates and subjected to thermal rearrangement to provide aUyl amines. The aUyl amine functionality was also accessible from enantio-selective reduction of propargyl ketones followed by conversion to the phthalamide derivative and reduction of the triple bond. Ozonolysis of these substrates provided the corresponding a-amino methyl esters in good yield (eq 48). As with the allyl alcohols, optically active substrates were treated with ozone without loss of enantiopurity of the chiral center. 

Two new syntheses of 2-pyridones have appeared. The first, involving condensation of ethyl 2-cyanoacrylates, e.g. ArCH=C(CN)C02Et, with an aryl or alkyl methyl ketone in the presence of ammonium acetate, furnishes 4-aryl-3-cyano-5-substituted and -5,6-disubstituted 2-pyridones in moderate yields (21—53%). The second method, which is particularly useful for 6-alkyl-2-pyridones (17 R = alkyl or aryl, R = alkyl), involves thermal rearrangement of the pseudourea (16), obtained by addition of secondary propargylic alcohols, e.g. R CH2CH(0H)C=CR, to 1-cyanopyrrolidine, in boiling xylene (Scheme 3). 

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