Pyrroles 2.3.5- trimethyl

Trimethyl-4-acetyl-pyrrol — 2,3,5-Trimethyl-4-athyl-pyrroln 80% d.Th. 

The synthesis has been modified to produce a series of porphyrin octaethanol derivatives (ethers) [162]. Pyrrole trimethyl ester (37) is selectively hydrolysed with sodium methoxide in methanol to give the diacid monoester (38), which is reduced (BH3/THF) and tosylated. The ditosylate was heated with the appropriate alcohol to afford the diether (with concommital transesterification of the pyrrolic a-ester). Oxidation with lead tetra-acetate gave compound 39, which was converted to the metal-free porphyrin in one pot by treatment with potassium hydroxide to hydrolyse the ester, hydrobromic acid to decarboxylate and cyclize, and chloranil to oxidize the macrocycle to the porphyrin (Scheme 44). 

Methyl pyrrole-l-carboxylate (14) and hot dimethyl acetylenedi-carboxylate give trimethyl pyrrole-1,3,4-tricarboxyIate (15) and acetylene, presumably through the addition-elimination sequence shown. Dimethyl acetylenedicarboxylate and 1-methylpyrrole com-... 

Methyl pyrrole-l-carboxylate and dimethyl acetylenedicarboxylate combine at 170°-200°C, giving trimethyl pyrrole-1,3,4-tricarboxylate (46) and acetylene. This reaction probably proceeds through the... 

Methylpyrrole and dimethyl acetylenedicarboxylate interact at 0°C to give a 1 2 adduct which is now known " to have structure (48). It is formed by addition of the ester across the 2,5-positions of the pyrrole yielding (47), which was not isolated but combined with a second molecule of the ester across the 2,7-positions accompanied by scission of the 4,7-bond as indicated. This adduct (48) was oxidized by bromine in methanol to trimethyl l-methylindole-2,3,4-tricarboxyl-ate and reacted further with hot dimethyl acetylenedicarboxylate. 

Besides the azo coupling reactions of 1-methyl- and 2,5-dimethylpyrrole with benzenediazonium-4-sulfonate mentioned above, Butler et al. (1977) synthesized almost all possible combination products of the unsubstituted and four 4-substituted benzenediazonium ions with pyrrole itself, with most isomeric mono-, di-, and trimethyl-pyrroles, and with 3-ethyl-2,4-dimethylpyrrole. These authors also investigated the kinetics of all these combinations (see Sec. 12.7). 

Dimethyl-4-athyl-2-formyl-pyrrol —> 2,3J-Trimethyl-4-athyl-pyrrol13 49% d.Th. 

Figure 11.11 Pyrogram of a paint sample collected from a decorative frame of the Universal Judgement by Bonamico Buffalmacco (fourteenth century, Monumental Cemetery of Pisa, Italy). Pyrolysis was performed with a microfurnace pyrolyser, at 600°C, in the presence of HMDS. 1, Benzene 2, ethyl acrylate 3, methyl methacrylate 4, acetic acid, trimethyl silyl ester 5, pyrrole 6, toluene 7, 2 methylpyrrole 8, 3 methylpyrrole 9, crotonic acid 10, ben zaldehyde 11, phenol 12, 2 methylphenol 13, 4 methylphenol 14, 2,4 dimethyl phenol 15, benzyl nitrile 16, 3 phenylpropionitrile 17, indole 18, phthalate 19, phthalate 20, ben zyl benzoate HMDS pyrolysis products [27]...

In this route a dihydroisoquinoline (58) is N alkylated with a highly functionalized o -bromoacetophenone (59) to give a quaternary salt (60), which is treated with base and cyclizes to a pyrroloisoquinoline (60). The pyrrole nucleus is then formylated under Vilsmeier-Haack conditions at position 5 and a proximate mesylated phenolic group is deprotected with base to yield a pen-tasubstituted pyrrole (61). Subsequent oxidative cyclization of this formylpyr-role produces the 5-lactone portion of lamellarin G trimethyl ether (36). This sequence allows for rapid and efficient analog synthesis as well as the synthesis of the natural product. 

Adsorption of a specific probe molecule on a catalyst induces changes in the vibrational spectra of surface groups and the adsorbed molecules used to characterize the nature and strength of the basic sites. The analysis of IR spectra of surface species formed by adsorption of probe molecules (e.g., CO, CO2, SO2, pyrrole, chloroform, acetonitrile, alcohols, thiols, boric acid trimethyl ether, acetylenes, ammonia, and pyridine) was reviewed critically by Lavalley (50), who concluded that there is no universally suitable probe molecule for the characterization of basic sites. This limitation results because most of the probe molecules interact with surface sites to form strongly bound complexes, which can cause irreversible changes of the surface. In this section, we review work with some of the probe molecules that are commonly used for characterizing alkaline earth metal oxides. 

Tetramic acids react with dimethyl orthoformate-A.A-dimethylamide 8 to give 3-(A,A-dimethylaminomethylidene) tetramic acids in almost quantitative yield. The latter route provides an access to compounds of the same type (80) (87TH1). With trimethyl orthoacetoacetate 81,2b forms pyrano[2,3-c]pyrrol 82 (91TH1). (See Figs. 37 and 38.)... 

The pyrrolo[3,2-6]pyrrole (118) is reported116 to result from thermolysis of the 12-7r-system 1,4,7-trimethyl-1,4,7-triazonine (117) in benzene or in the vapor phase. This interesting reaction proceeds with extrusion of methylamine, but the mechanism is uncertain. 

Although it is more usual to obtain the halogenoacyl derivatives of pyrrole and indole by direct acylation (see Section 3.05.1.2.6), it is possible to carry out electrophilic halogena-tion of acylindoles <79HC(25-3)357). 3,4-Diacetyl-l,2,5-trimethylpyrrole has also been reported to react with phenyltrimethylammonium tribromide to give the 3,4-bis(bromoacetyl) derivative, which cyclizes in the presence of a zinc-copper catalyst to yield 4,5,6,7-tetrahydro-l,2,3-trimethyl-4,7-dioxoisoindole (74CC1034). 

---