Alkyne From epoxy ketone

Eschenmoser-Tanabe fragmentation Formation of alkynals or alkynones from epoxy ketone hydrazones. 158... 

The first examples to demonstrate the synthetic power of this method were the preparations of exal-tone (118) and muscone (119), starting from the a,p-unsaturated ketones (135) and proceeding via the epoxy ketones (136), the tosylhydrazones of which are cleaved to the cycloalkynones (137 Scheme 44). A little later, Tanabe described the same reaction type starting from epoxydecalones, using this fragmentation for the synthesis of secosteroid alkynic ketones. ... 

During modei studies for the synthesis of botrydiane sesquiterpene antibiotics, B.M. Trost and co-workers prepared a compiex 1,6-enyne precursor for transition metal catalyzed enyne metathesis reactions. The 1,6-enyne was prepared from a heavily substituted alkynal, which was synthesized via the Eschenmoser-Tanabe fragmentation of an epoxy ketone. The resulting alkynal was unstable, so it was immediately subjected to a Wittig oiefination to afford the desired 1,6-enyne. 

Oxidation of allenes and alkynes. The oxidation promoted by cetylpyri-dinium peroxotungstophosphate in an alcoholic solvent produces a-alkoxy ketones from allenes and a,/3-epoxy ketones from alkynes (along with a,/3-unsaturated ketones). Diphenylacetylene gives benzil (93% yield at 45% conversion). 

In 1973, it was demonstrated that 1,2-epoxystannanes, produced from vinylstannanes and MCPBA, could be isolated and characterized, in comparison widi 2,3-epoxystannanes (from allylstannanes), which are extremely reactive and have not been isolated (see Section 4.2.2.3). Subsequently, useful applications of 1,2-epoxy stannanes have been reported, including the internal alkyne ketone conversion, in the caibapenem and carbacephem 0-lactam antibiotic) skeletons. Ketone (10) should be of value in the construction of the biologically interesting l-carbapen-2-ene ring system. Synthesis of ketoacetates of potential use in the carbacephem system (e.g. 11 and 12) was also achieved by similar sequences shown in Scheme 11. ... 

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