L-Telluracyclohexa-2,5-diene-4-ones

The addition of telluride anion to l-(trimethylsilyl)penta-l, 4-diyn-3-ones apparently represents a general method for the preparation of 2-substituted l-telluracyclohexa-2,5-dien-4-ones 22 (92MI3). In actual fact, the reaction of l-(trimethylsilyl)-5-phenylpenta-l,4-diyn-3-one with telluride anion affords 22 (R1 = Ph, R2 = H) in 38% yield, whereas only 12% of this compound is attained in the reaction with l-phenylpenta-l,4-diyn-3-one (87JOC3662). 

Like other dicoordinate tellurium compounds, l-telluracyclohexa-2,5-dien-4-ones 22 smoothly add halogens (chlorine, bromine, and iodine) affording cr-telluranes 31 in rather high yields. When treated with a peroxy acid, compounds 22 form 1,1-diacetoxy derivatives 31 (87JOC2123). 1-Tellurapyranylidenomalondinitriles 30 undergo similar transformations. 

According to X-ray structural data (92MI3), l-telluracyclohexa-2,5-dien-4-one is planar. No substantial intermolecular interaction between... 

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