Ramburg-Backlund reaction

Cyclic enediynes.4 A Ramburg-Backlund reaction of the cyclic diynes 1 furnishes cyclic enediynes. 

Ring-contraction procedures for generating a four-membered ring fused to a six-membered ring include the application of the Ramburg-Backlund reaction to the synthesis of the hetero-propellanes (357 X = O or SOj), electrocyclic ring closure in the synthesis of the propellanes (358 X = O or NMe), and sensitized photo-oxidation of the olefin (359) in the synthesis of (360). 

Chem. Lett. 1984, 833-836. For another variation of the Ramburg-Backlund reaction see Matusuyama, H. Miyazawa, Y. Kobayashi, M. Regioselective Alkylation and the Ramberg-Baecklund Type Reaction of a-( -tolylsulfonyl)thiane S,S-Dioxide. A New Route to the Synthesis of 3-Alkyl-3-Cyclopentenones Chem. Lett. 1986, 433—436. 

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