The addition of reactive carbanions to a6-benzenetricarbonyIchromium(0) produced ~'-(6-alkylcyclohexadienyl)tricarbonylchromium(0) anion complexes, as the lithium salts. Reaction with a variety of oxidizing agents (iodine, cerium(lV), oxygen) removes the hydrogen from C-6 and detaches the C r ( C 0 ) 3 unit, to produce a substituted arene. Reaction with electrophiles (potential hydride acceptors) leads to cleavage of the carbon-carbon bond at C-6 with regeneration of qh-benzenetricarbonylchroniium(0). Solution spectral ( ' H N MR, IR) data are consistent with a n g'-cyclohexadienyl structure. X-ray diffraction analysis on the crystalline adduct of qh-benzenetricarbonyIchromium(0) and 2-lithio-l,3-dithane defines the mode of addition (exo), the deformation (38.6') of C-6 from the plane of carbons 1-5 in the cyclohexadienyl ligand. and the preferred conformation of the C r ( C 0 ) 3 unit.

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Phenoxybenzenes and phenoxypyridines were prepared and tested for the effect of substituents on antipicornavirus activity. The most active compound, 2-(3,4-dichlorophenoxy)-5-nitrobenzonitrile (8), demonstrated broad-spectrum antipicornavirus activity. Compound 8 and several analogues each given orally prior to and during infection protected mice against an otherwise lethal challenge with coxsackievirus A21.

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The 6-substituted 2-(3',4'-dichlorophenoxy)-2H-pyrano[2,3-b]pyridines MDL 20,610 (6-SO2CH3), MDL 20,646 (6-Br), and MDL 20,957 (6-Cl) are potent antirhinovirus compounds with median plaque 50% inhibitory concentrations (IC1/2s) of 0.03, 0.006, and 0.006 micrograms/ml, respectively, against the 32 serotypes evaluated. The 6-halogenated analogs produced 99% reductions in progeny virion yields at concentrations as low as 0.004 micrograms/ml. However, these analogs perturbated HeLa cell metabolism at lower concentrations (at or above 5 micrograms/ml) than did the 6-methylsulfonyl analog (at or above 20 micrograms/ml). Compound MDL 20,610 was also active against human, simian, and bovine rotaviruses (cytopathic effect IC1/2s of 0.8 to 1.5 micrograms/ml) and possessed variable enterovirus and paramyxovirus activity.