Abstract
The reactions of 1,8-diiodonaphthalene with the enolate ions from pinacolone and acetone, and with p-toluenethiolate, mesitylenethiolate, and diethylphosphite ions in DMSO or liquid ammonia have been studied. In these SRN1 (or related radical) processes, disubstitution, without isolation of the monosubstituted monoiodo compound takes place with the enolate ions to give ultimately (after a subsequent aldol condensation) substituted dihydrophenalenes. With ptoluenethiolate ion a novel thiaxanthene system results. With mesitylenthiolate ion and diethylphosphite ions, monosubstitution with monoreduction occurs. Deuterium labeling experiments show that the major source of hydrogen (deuterium) necessary for the reduction process arises from DMSO by a radical abstraction reaction.
Highlights
The SRN1 radical chain substitution mechanism, first recognised in aromatic nucleophilic substitutions in 1970,1 is a well-established mechanism for substitution reactions in aryl halides and dihaloarenes.[2]
The SRN1 mechanism for substitution in dihaloarenes is represented in Scheme 1
The peri relationship of the iodo groups of 1 cause some interesting effects in its SRN1 reactions with the enolates 2 and 3, the thiolates 4, 5a, 5b and 5c, and the phosphite 6 when compared with the corresponding reactions of o-dihalobenzenes with these nucleophiles
Summary
The SRN1 radical chain substitution mechanism, first recognised in aromatic nucleophilic substitutions in 1970,1 is a well-established mechanism for substitution reactions in aryl halides and dihaloarenes.[2] The SRN1 mechanism (nucleophile-initiated) for substitution in dihaloarenes is represented in Scheme 1 (equations 1-7). A variety of nucleophiles have been used in these reactions, including ketone enolates,[3] aromatic thiolates[4,5] and dialkylphosphites.[6]. The SRN1 reactions of a dihalogenated system in which the halogens are on different rings in a fused polycyclic aromatic system appear to be unreported. The proximity of the two iodines in 1 might lead to interesting steric or chemical interactions between the incoming nucleophiles or other interesting interactions during the various SRN1 reaction steps. This paper reports the reaction of 1 with the potassium enolates 2 and 3, sodium p-toluenethiolate 4, sodium and potassium mesitylenethiolate 5a and 5b and the potassium salt of its deuterated derivative 5c, and potassium diethylphosphite 6
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