Pyrroles, 1-substituted, synthesis through

A dual catalyst system piperidine-iodine was used in the synthesis of 3-substituted coumarins through a one-pot three-component reaction of salicylaldehyde derivatives, P-keto esters, and l-(2-aminophenyl)pyrrole in DMF at room temperature (14T2048) and through a four-component reaction of salicylaldehyde derivatives, P-keto esters, ammonium acetate, and isatoic anhydride in DMF at 60°C (Scheme 55) (14SL1596). 

Scheme 15.100 1,2,5-Substituted pyrrole synthesis through the tandem...

A highly stereoselective synthesis of 3-pyrrole-substituted fi-lactams 15 and 16 is reported via -lactams 13 and 14 obtained through treatment of imines 11 derived from N-phenyl, p-methoxyphenyl, or 6-chrysenyl amine with phthalimido acetic acid 12 and deprotection of phthalimido group by ethylenediamine, respectively [42]. The polyaromatic imines derived from 6-chrysenyl amine produced (+)-tra s isomer exclusively (Scheme 3.8). The electron-withdrawing aromatic groups at the C- and N-termini of the imine led to the formation of the trans isomer. The formation of trans isomer in the case of N-chrysenyl imines and N-diaryl imines... 

Synthesis of pyrroles from ketones (through ketoximes) and propyne-allene mixture, a large-scale side product of hydrocarbons pyrolysis, essentially expands the preparative possibilities of the Trofimov reaction. 5-Methyl-substituted pyrroles, having diverse substituents in the positions 2 and 3, become readily available for the first time. 

Often, in the synthesis of natural products containing the indolizidine substructure, it is necessary to modify a preformed indolizidine ring. This is the case in the synthesis of (+)-myrmicarin 217 191 where the key step is the closure of the third ring through an electrophilic substitution on the pyrrole nucleus (Scheme 45) <2000JOC2824>. 

Methoxyethyltosylamide also participates in the [3 -I- 2] addition reaction with 102, although it does not give any of the expected dihydropyrrole derivative 104. Instead, the major product was found to be pyrrole 105, which presumably results through ready elimination of methanol from the putative intermediate 104. Thus, this addition holds promise for the synthesis of 2-substituted tosylpyrroles (Scheme 29). In addition to 105, a minor product 106 (12%) is also formed in this reaction. 

Kende described an impressive example of the use of the [34-4] cycloaddition in natural product synthesis (Scheme 14.10) [101]. A key nortropinone intermediate for the total synthesis of ( )-isostemofoHne 105 was acquired through the tropane system 104, which was formed from the [34-4] cycloaddition of pyrrole 103 and a siloxy-substituted vinylcarbenoid of 87 in 90% yield. 

In addition to Scheme 20, the synthesis of (5,(5 -substituted pyrroles has also been achieved through a Zard-Barton reaction (1985JCS(CC)1098, 1990T7587, 1991SL127). Likewise, Hayashi et al. (03OL2845, 03IC7345)... 

Polypyrroles (PPy s) are formed by the oxidation of pyrrole or substituted pyrrole monomers. In the vast majority of cases, these oxidations have been carried out by either (1) electropolymerization at a conductive substrate (electrode) through the application of an external potential or (2) chemical polymerization in solution by the use of a chemical oxidant. Photochemically initiated and enzyme-catalyzed polymerization routes have also been described but are less developed. These various approaches produce polypyrrole (PPy) materials with different forms—chemical oxidations generally produce powders, whereas electrochemical synthesis leads to films deposited on the working electrode, and enzymatic polymerization gives aqueous dispersions. The conducting polymer products also possess different chemical/electrical properties. These alternative routes to PPy s are therefore discussed separately in this chapter. 

Bromodimethylsulfonium bromide (BDMS)-catalyzed synthesis of substituted pyrroles through a one-pot four-component reaction. 

M. Lai, P. R. Bagdi, R. S. Basha, P. Saravanan, S. Patra, A. T. Khan, Tetrahedron Lett. 2012, 53, 4145 150. Synthesis of tetra-substituted pyrroles, a potential phosphodiesterase 4B inhibitor, through nickel(It) chloride hexahydrate catalyzed one-pot four-component reaction. 

Intramolecular nitrogen attack in propargylated enaminones allows silver-catalyzed access to functionalized pyrroles. This Ag-promoted hydroamination can also be used to obtain A bridgehead pyrroles. Silver nitrate-mediated cyclization of allenylamines, available from Uthiated alkoxy allenes and imines or through reaction of l-(lV-carbamoyl)-alkylcuprates with propargyl substrates, provides access to 2,5-dihydropyrrole derivatives. Iminoallenes can be used for the synthesis of substituted p)moles in moderate yields in the presence of potassium carbonate. ... 

Many authors agree that products with one or more nitrogen groups as substitutes of the oxygen atoms in the squarate 2 ion should be called rather squaraines. The first of this class of compounds was prepared in 1965 through the reaction of squaric acid 6 and pyrroles, which produced intensely colored condensation products [62]. But the literature also describes the synthesis of a squaraine obtained from resorcinol, which does not possess nitrogen atoms therefore, there is no consensus on the concept of squaraines in the literature [63]. 

Chiba and coworkers developed a Cu(NTf2)2-catalyzed synthesis of pyrroles from a-ethoxycarbonyl vinyl azides and ethyl acetoacetate through the 1,4-addition reaction of the acetoacetate to the vinyl azides [19]. Jiao and coworkers reported a copper- or nickel-catalyzed highly selective denitrogenative annula-tion of vinyl azides with acetaldehydes to 2,4- and 3,4-diaryl-substituted pyrroles. Cu(OAc)2 could catalyze the formation of 2,4-diaryl-substituted pyrroles. This selective polysubstituted pyrrole synthesis could proceed under mild conditions without any acidic or basic conditions [20] (Scheme 8.8). 

Recently, Guan et al. developed a novel Cu(OAc)2-promoted oxidative coupling of enamides with electron-deficient alkynes for the synthesis of multisubstituted NH pyrroles. This reaction tolerates a wide range of functional groups and is a reliable procedure for the rapid elaboration of readily available enamides into a variety of diester-substituted NH pyrroles. The reaction proceeded through C-H and N-H bond functionalization of enamides CU/O2 system [22]. They also developed an efficient CuBr-catalyzed homocoupling of ketoxime carboxylates for the synthesis of symmetrical pyrroles [23] (Scheme 8.10). 

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