Sodium pyrrolate, reaction with metal

Selective Birch reductions were investigated with a number of electron-rich fused pyrrole substrates <05JOC2054>. Deprotonation of phenol 79 followed by treatment of phenoxide 80 with sodium metal in ammonia gave 81. The same reaction with the corresponding 7-methoxy derivative gave a mixture that contained over-reduced products. 

Pyrrole carbinols were identified as new base-labile protecting groups for aldehydes. The optimal bases for the preparation of a pyrrole carbinol via the reaction of metal pyrrolates with iso-butyraldehyde were sought. Alkali metal pyrrolates performed better than their alkaline earth counterparts. Lithium and sodium pyrrolates prepared via the deprotonation of pyrrole with n-BuLi, LHMDS, andNaHMDS afforded the corresponding pyrrole carbinol in 90%, 85% and 85% )fields, respectively, whereas potassium... 

Reaction of the parent heterocycle with arenesulfonyl chlorides in the presence of a suitable base constitutes the only widely applied method for the Marylsul-fonylation of indoles, pyrroles, imidazoles, etc. Three procedures using indoles illustrate the variety of conditions. Typical bases include n-BuLi [Scheme 8.268]515 or a metal hydride [Scheme 8.269]524 in THF, or phase-transfer catalysis using sodium hydroxide in aqueous dichlorome thane [Scheme 8.270].515... 

Incorporation of metal ions into porphyrins is affected by other compounds in solution. Lowe and Phillips (25) found that copper(II) ions were chelated with dimethyl protoporphyrin ester 20,000 times faster in 2.5% sodium dodecylsulfate (SDS) than in 5% cetyl trimethyl ammonium bromide (CATB). The increased activity of SDS treated porphyrin was attributed to electrostatic attraction between anionic micelles formed around the tetrapyrrole nucleus and the metal cation. The authors also reported the influence of certain chelating agents on the rate of copper complex formation. Equimolar concentrations of copper and 8-hydroxyquinoline or sodium diethylthiocarbamate in 2.5% SDS increased the reaction rate 38 and 165 times, respectively, above the control. Secondary chelators may act by removing the hydration sphere on the metal ion increasing its attraction to pyrrole nitrogens (26). 

Azacyclopentadienyl complexes may be obtained by the reaction of the anion of pyrrole (sodium or potassium salt) with transition metal compounds [equations (9.101) and (9.102)]. 

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