1-Methylpyrrole, with

A kinetic and product study of the dichloroacetic acid (DCA) catalyzed chlorination of 1-methylpyrrole with a series of 3- and 4-substituted A -chlorobenzamides 325 under nitrogen, at 40 °C was carried out (Scheme 73) <2003T2125>. Chlorination at C-2 of the pyrrole ring leads to the formation of 2-chloro-l-methylpyrrole 326 and subsequently 2,5-dichloro-l-methylpyrrole 327. The total yield of attack at C-2 is therefore the sum of the yields of pyrroles 326 and 327. The yields of 2-chlorination (ca. 84%) and 3-chlorination (ca. 2.6%) were essentially constant as... 

Reactions of pyrrole or 1-methylpyrrole with N-aroylbenzotriazoles (ArCO = 4-MeCgH4CO, 4-O2NC6H4CO, 4-Et2NC6H4CO, 2-furoyl, 2-pyridoyl, 2-indolcarbonyl, 2-pyrroloyl) in the presence of TiCU afford 2-acylpyrroles in yields from 21% to 94%. In contrast, l-(triisopropylsilyl) pyrrole under the same conditions gives the corresponding 3-acyl-substituted pyrroles (03JOC5720). 

Comparison of the reaction conditions prescribed for the alkylation of 2-lithio-1-methylpyrrole with those applied in the reaction of 2-lithiothiophene with butyl bromide suggests that the former reacts more smoothly (compare Exp. 3). Since further experimental data is lacking, it cannot be said whether this difference in... 

The cycloaddition reaction of 1-methylpyrrole with nitrileimine (AcC WPh) afforded (34) (Table 4) along with another cycloadduct (189) <72TL4703>. The tricyclic product (31) (Table 4) was formed by hydrazinolysis of the fluoride salt (190) <74Mi 835-01 >. 

The reaction of pyrrole with dichlorocarbene proceeds in part via a dichlorocyclo-propane intermediate, ring expansion of which leads to 3-chloropyridine." There are relatively few (section 14.1.2) reported isolable cyclopropane-containing adducts from pyrroles - l-methoxycarbonylpyrrole ° or N -acylpyrroles. 1-Methylpyrrole with ethoxycarbonylcarbene gives only substitution products. " ... 

The 2,5-diarylation of thiazole can be carried out effectively with a bulky phosphine ligand. In this case, no monoarylated product is observed, even in the early stage of the reaction, which suggests that the second arylation proceeds relatively rapidly (Equation 10.62) [95]. The selective 2-arylation of thiazole is accomplished by using Cul and BU4NF as cocatalyst and base, respectively (Equation 10.63) [96]. By using Pd(OH)2/C as catalyst, the 5-position can be arylated selectively (Equation 10.64) [97]. The palladium-catalyzed arylation of thiazole as well as 1-methylpyrrole with a polymer-Unked aryl iodide has been reported [98]. 

The reaction is analogous to the bakelite poly condensation. It is difficult to halt this reabction at an early stage, but pyrrole is said to react with formalin and a trace of hydrochloric acid, and with other aliphatic aldehydes in the presence of zinc chloride, to give dipyrrylmethanes . If the reaction of pyrrole or 1-methylpyrrole with formalin is carried out in the presence of... 

Frontier orbital theory predicts that electrophilic substitution of pyrroles with soft electrophiles will be frontier controlled and occur at the 2-position, whereas electrophilic substitution with hard electrophiles will be charge controlled and occur at the 3-position. These predictions may be illustrated by the substitution behaviour of 1-benzenesulfonylpyr-role. Nitration and Friedel-Crafts acylation of this substrate occurs at the 3-position, whereas the softer electrophiles generated in the Mannich reaction (R2N=CH2), in formylation under Vilsmeier conditions (R2N=CHC1) or in formylation with dichloromethyl methyl ether and aluminum chloride (MeO=CHCl) effect substitution mainly in the 2-position (81TL4899, 81TL4901). Formylation of 2-methoxycarbonyl-l-methylpyrrole with... 

The dimer of 1-methyl- -pyrroline (39) was obtained by reduction of N-methylpyrrole with zinc and hydrochloric acid (132) and, together with the trimer, by mercuric acetate dehydrogenation of N-methylpyrrolidine (131). J -Pyrroline-N-oxides form dimers in a similar manner (302). Treatment of 1,2-dimethyl-zl -piperideine with formaldehyde, producing l-methyl-3-acetylpiperidine (603), serves as an example of a mixed aldol reaction (Scheme 18). 

The copper-catalyzed decomposition of diazoacetic ester in the presence of pyrrole was first described in 1899 and later investigated in more detail by Nenitzescu and Solomonica. Ethyl pyrrole-2-acetate (13), the normal product of electrophilic substitution, was obtained in 50% yield and was degraded to 2-methylpyrrole. Similarly iV -methylpyrrole with two moles of diazoacetic ester gave, after hydrolysis, the 2,5-diacetic acid (14) while 2,3,5-trimethylpyrrole gave, after degradation, 2,3,4,5-tetramethylpyrrole by substitution of ethoxycarbonylcarbene at the less favored )3-position. Nenitzescu and Solomonica also successfully treated pyrroles with phenyl-... 

IV-Methylpyrrole with (Cp IrH3)2 and 3,3-dimethyl-1-butene gives a couple of unique organometallic products, 86 and 87 (990M134). In 86, the C—H bond in position 2 is activated and a rare tiVC) ti (C=C) coordination mode is realized. Species 87 is a zwitterionic compound containing a triple bond between the iridium atoms. 

New electrophilic substitution reaction methods for the preparation of dipyrromethanes have been reported. The condensation of IV-methylpyrrole with benzaldehyde leading to the corresponding dipyrromethane was promoted by the addition of the organic catalyst, pyrrolidinium tetrafluoroborate <06T12375>. The reaction between pyrrole and N-tosyl imines promoted by metal triflates gave dipyrromethanes whereas tripyrromethane byproducts were not observed <06T10130>. 

In most cases, the oxidative addition process consumes stoichiometric amount of Pd(OAc>2. One of the earliest examples of the use of palladium in pyrrole chemistry was the Pd(0Ac)2 induced oxidative coupling of A-methylpyrrole with styrene to afford a mixture of olefins 18 and 19 in low yield based on palladium acetate [28]. 

Formylation of 2-methoxycarbonyl-l-methylpyrrole with dichloromethyl methyl ether and aluminum chloride occurs in the 4-position, while under Vilsmeier conditions the main product is the 5-formyl derivative (78JOC4849). 

Addition reactions of 2-substituted N- methylpyrroles with C- acetyl-TV- phenylnitrilimine gave double cycloaddition products, spiro-cycloadducts and noncyclic bis-adducts (78JHC293). 

Chlorination with. Y-clilorosiiccinimide is less selective. 1-Methylpyrrole reacts with Ar-chloroimidcs to give 76 in which the imidyl group is attached to C(2) the 2-chloro compound is proposed as an intermediate (Scheme 28). Chlorination of 2-methylpyrrole with A - ch I or o b en z a mi d c s, catalyzed with dichloroacetic acid at 40 C, proceeds cleanly at C(2) and then further to give the 2,5-dichloropyrrole <2003T2125>. 

Carbonsulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol 446. If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. In the pyrrole series, a 2-thiol and the corresponding selenol can be prepared via reaction of 2-lithio-l-methylpyrrole with sulfur or selenium, then trapping with Me3SiCl leading to the 2-Me3SiX-substituted derivatives <1997T13079>. 

Dry AT-methylpyrrole with CaS04, then fractionally distil it from KOH immediately before use. [Beilstein 20 Ill/lV 2080, 20/5 V 8.]... 

Treatment of 2-methylpyrrole with HCl produces a dimer, not a trimer as does pyrrole itself. Suggest a structure for the dimer, C10H14N2, and explain the non-formation of a trimer. 

Reactions of Pyrroles. 1,3-Di-t-butylpyrrole forms the first stable protonated pyrrole, the salt (104). Electrophilic substitution of pyrrole with MeaC or Me FC in the gas phase occurs mainly at the j3-position, as does nitration and Friedel-Crafts acylation of l-phenylsulphonylpyrrole2 Pyrrole-2,5-dialdehyde has been prepared by Vilsmeier-Haack formylation of the ester (105), followed by hydrolysis. A similar method has been used to convert the di-acetal (106) into pyrrole-2,3,5-tricarbaldehyde. AT-Benzoyl-pyrrole reacts with benzene in the presence of palladium(II) acetate to yield a mixture of l-benzoyl-2,5-diphenylpyrrole, the bipyrrolyl (107), and compound (108). Treating lithiated A-methylpyrrole with nickel(II) chloride results in the polypyrrolyls (109 = 0-4). 2-Aryl-1-methylpyrroles are obtained by cross-coupling of l-methylpyrrol-2-ylmagnesium bromide with aryl halides in the presence of palladium(0)-phosphine complexes. ... 

A new route to tropane derivatives involving reaction of aao a -tetrabromoacetone with N-methoxycarbonylpyrrole and di-ironenneacarbonyl was described in Volume 5. 6,7-Dehydronortropinone derivatives (13) can also be obtained in good yields from aa -dibromoketones and pyrroles (or N-methylpyrroles) with copper and sodium iodide. ... 

---