Neuronal nicotinic acetylcholine receptors are members of the ligand-gated ion channel receptor superfamily and may play important roles in modulating neurotransmission, cognition, sensory gating, and anxiety. Because of its distribution and abundance in the CNS, the alpha 7 nicotinic receptor is a strong candidate to be involved in some of these functions. In this paper we describe the synthesis and in vitro profile of AR-R17779, (-)-spiro[1-azabicyclo[2.2. 2]octane-3,5'-oxazolidin-2'-one] (4a), a potent full agonist at the rat alpha 7 nicotinic receptor, which is highly selective for the rat alpha 7 nicotinic receptor over the alpha 4 beta 2 subtype. Preliminary SAR of AR-R17779 presented here indicate that there is little scope for modification of this rigid molecule as even minor changes result in significant loss of the alpha 7 nicotinic receptor affinity.

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2.3.5.6-Tetrafluoro-4-iodopyridine, prepared by oxidation of 2.3.5.6-tetrafluoro-4-hydrazinopyridine in the presence of methyl iodide or, preferably, by reaction of pentafluoropyridine with sodium iodide in dimethylformamide, is readily converted into 2.3.5.6-tetrafluoropyridylrnagnesium iodide or 2,3,5,6-tetrafluoropyridyllithium ; some reactions of these organometallic compounds are described. Hydroxide ion, methoxide ion, and ammonia attack 2.3.5.6-tetrafluoro-4-iodopyridine at the 2-position, to give the corresponding 2-substituted trifluoro-4-iodopyridines, but iodide ion appears to attack the 4-iodo-substituent with the formation of the 2.3.5.6tetrafluoropyridyl anion. Coupling of tetrafluoro-4-iodopyridine by the Ullmann technique affords perfluoro-4.4'-bipyridyl. Reaction of 3-chloro-2,4,5,6-tetrafluoropyridine with sodium iodide in dimethylformamide yields 3-chloro-2.5.6-trifluoro-4-iodopyridine.Chester Institute of Science and Technology, Manchester 1 ~,~,~,~-TETRAFLUORO-~-IODOPYRIDINE, a low-melting pentafluorophenylhydrazine into pentafluoroiodobenzsolid, can be prepared by oxidation of 2,3,5,6-tetrafluoro-ene 3, or, preferably, by direct nucleophilic displace-4hydrazinopyridine with silver oxide in the presence ment of the activated 2*4 4-fluorine in pentafluoropyridine of an excess of methyl iodide (cf. the conversion of by iodide (anhydrous sodium iodidein dimethylfonnamide preceding Paper.