Cycloaddition and Heterocyclization Reactions of Acetylenic Compounds with Electron-Withdrawing Substituents

1 CYCLOADDITION AND HETEROCYCLIZATION REACTIONS OF ACETYLENIC COMPOUNDS WITH ELECTRON-WITHDRAWING SUBSTITUENTS 

These compounds include trifluoroacetylacetylene 4.976, 1-trifluoro-acetyl-2-trimethylstannylacetylene 4.977, l-trifluoroacetyl-2-haloacety-lenes, 4.978a,b 1-trifluoromethyl- and l-perfluoroethylacetylene-2-phosphonates 4.979, 4.980, l-chloroacetylene-2-phosphonates 4.981, 

Alkynes in Cycloadditions, First Edition. Maretina I. Alexandrovna. 

The best yield was achieved by the following method. Following the reaction of diethyl methylphosphonate and perfluorinated carboxylic ester, a 69 mmol solution of the resultant ketone-enol mixture was added to 100 mL of anhydrous methylene chloride. It was then cooled to -40°C (nitrogen), diisopropylmethylamine 32.1 g (248 mmol) was quickly added, and after 10 minutes stirring, 23.4 g (83 mmol) tri-fluoromethanesulfonic anhydride was added dropwise at -30°C. The suspension was kept for 3 hours at —30°C and 3 hours at 5—7°C, then 

Dibromoacetylene, which is produced in the reaction of acetylene with aqueous sodium or potassium hypobromide, may be used in a similar way. 

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