Pyrroles reaction with acetone

The acid-catalyzed addition of aliphatic ketones to 2,3,4- or 2,3,5-trisubstituted pyrroles generally produces bispyrrolylalkanes, analogous in structure to the products of the corresponding reactions with aldehydes, whereas 2,5-disubstituted pyrroles react with acetone to form a 2 3 adduct (113). Pyrrole and 3,4-disubstituted pyrroles react with aliphatic ketones to give porphyrinogens (114), which, unlike the macrocycles obtained from the... 

Pyrroles react with the conjugate acids of aldehydes and ketones to give carbinols (e.g. 67) which cannot normally be isolated but which undergo proton-catalyzed loss of water to give reactive electrophiles (e.g. 68). Subsequent reaction may lead to polymeric products, but in the case of reaction of pyrrole and acetone a cyclic tetramer (69) is formed in high yield. 

The increase in yield of 15 a from ca 20% to over 40% in the presence of lithium perchlorate 77) has led to the suggestion of a template effect. However, recent experiments78) indicate that the higher yields correlate not with the metal ion but with the acidity of the reaction medium. In similar fashion, thiophene and pyrrole undergo acid-catalyzed condensations with acetone to yield 16 m> and 17 81). Benz-aldehyde also condenses with pyrrole 82but the initially formed compound loses six hydrogens to form the planar tetraphenylporphin 18. 

For example, irradiation of 2-iodothiophene-5-carboxaldehyde with phenyl acetylene and styrene yields (127) and (128), respectively. In what may be a related reaction irradiation of pyrrole with acetone is reported to yield a tetrapyrrole. ... 

Baeyer first reported a 4 4 cyclization product for the reaction of pyrrole and dry acetone catalyzed by the addition of one drop of hydrochloric acid (Baeyer, 1886). The macrocycle was later isolated in an 88% yield in a less violent reaction (Rothemund and Gage, 1955). Metal derivatives of the phthalocyanines were obtained when o-diaminobenzene, o-cyanobenzamide, or related compounds were pyrolized with metals or their salts (Braun and Tcherniac, 1907). This was possibly the first observed template synthesis of a macrocyclic ligand. 

Propanone (acetone) carbon acidity, 10 protection of diols as "acetonides , 158, 266-267, 276-277, 321, 322 reaction with pyrrole, 250-251 Propanoyl chloride, 2- acetyloxy)-2-methyI-(Moffatt s reagent) O-protection, 160 chlorohydrtns from diols, 160, 327-328 2-Propenal (acrolein, acrylaldehyde) pr., 174... 

Robinson s synthesis of tropine (210) on the other hand was as direct (two steps) as Willstatter s was long but it involved the use of the very sensitive succinic dialdehyde (from pyrrole) (157, 219). The fragments from the hypothetical fission of the symmetrical tropinone (XLVI) suggested to Robinson the possibility of obtaining this ketone by the condensation of succinic dialdehyde and methylamine with acetone. The primary reaction was considered to be the combination of succinic dialdehyde with methyl-amine and the resulting biscarbinolamine (XLIX) in turn condensed with acetone. This synthesis was realized when these reactants, in aqueous... 

Treibs and Ohorodnik [4] prepared this ring system by the reaction of ethyl 2-methyl-4-hydroxypyrrole-3-carboxylate (IV) with ethyl acetoacetate (EAA) in the presence of sodium ethoxide and in this way ethyl 2,6-dimethyl-7-oxopyrano[3,2-b]pyrrole-3-carboxylate (V) was prepared. A similar reaction of (IV) with acetone dicarboxylic ester (ADE) gave (VI), but, no yields were given for either reaction. 

New calix[4]pyrroles 145 bearing dipyrrolylquinoxaline as strapping elements have been synthesized (Kim et al. 2009). The synthesis of receptor 145 starts with ketone 142, a species that was prepared by the reaction of oxalyl chloride with 2 equivalents of 2-(3-oxobutyl)pyrrole (Yadav et al. 2001). Once in hand, 142 was reacted with 4-nitro-1,2-DAB in the presence of acid to afford bisketone 143 in 24 % yield (Black et al. 1999 Anzenbacher et al. 2000). Treatment of this latter intermediate with neat pyrrole in the presence of trilluoroacelic acid afforded the bis-dipyrromethane 144 in 74 % yield (Scheme 5.34). While this procedure proved effective, attempts to effect the direct alkylation of 6-nitro-2,3-di(2 -pyrrolyl)qui-noxaline with methyl vinyl ketone produced only trace quantities of the desired product 144. Acid-catalyzed condensation of 144 with acetone then gave the... 

Reaction of Ni(CN)2NH3(pyrrole) (III), with Fe3+. 0.20g (1 mmole) of Ni(CN)2NH3(pyrrole) were suspended in an aqueous solution of 0.8g (5 mmole) of FeCl3. The mixture was stirred at room temperature for 1.5 hs and the black solid was isolated by filtration, washed with H2O and acetone and dried in vacuum. Elemental analysis suggests the formula [Ni(CN)2NH3] (C4H2NH)Clo.22lo.9 (V). The same... 

The one-electron reduction of thiazole in aqueous solution has been studied by the technique of pulse radiolysis and kinetic absorption spectrophotometry (514). The acetone ketyl radical (CH ljCOH and the solvated electron e were used as one-electron reducing agents. The reaction rate constant of with thiazole determined at pH 8.0 is fe = 2.1 X 10 mole sec in agreement with 2.5 x 10 mole sec" , the value given by the National Bureau of Standards (513). It is considerably higher than that for thiophene (6.5 x 10" mole" sec" ) (513) and pyrrole (6.0 X10 mole sec ) (513). The reaction rate constant of acetone ketyl radical with thiazolium ion determined at pH 0.8 is lc = 6.2=10 mole sec" . Relatively strong transient absorption spectra are observed from these one-electron reactions they show (nm) and e... 

The /3-electrophilic additions of pentaamineosmium(ll) complexes bearing various 4,5-tf -coordinated pyrroles to carbonyl compounds have been reported by Harman and co-workers (Scheme 78). 1 1-Methylpyrrole complex, when reacted with benzaldehyde or its dimethylacetal in the presence of /-butyldimethylsilyl triflate (TBSOTf), afforded the corresponding aldol adduct 177 as a 1 1 ratio of diastereoisomers. Pyrrole, 1-methylpyrrole, or 2,5-dimethylpyr-role osmium complexes reacted with an excess of acetone in the presence of TBSOTf to give the O-silylated 377-pyrrolium aldol adducts 178, which may serve as intermediates for various other reactions. 

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