3.4- Dimethylpyrroles, reaction with

Reaction of lithium 2,5-dimethylpyrrolate ion with [RhCl(CO)2]2 leads to formation of 84 (88PAC1193 90P1503). This is the first example of the mixed mode, when the ti N) and ti (C=C) coordination are realized simultaneously. Nucleophilic addition of triphenylphosphine and triphenylarsine gives 85 (E = P, As). The iridium analogs of 84 and 85 have also been synthesized. 

It has long been known that pyrroles can be used as coupling components (see, for example, Schofield, 1967, p. 76). More recently Butler and coworkers have studied the reactions of arenediazonium ions with pyrroles (Butler et al., 1977 Butler and Shepherd, 1978, 1980). 1-Methyl- and 2,5-dimethylpyrrole react with diazotized sulfanilic acid to give 12.34 and 12.35 respectively. The formation of 12.34 is in accordance with the a-positions in pyrrole being more susceptible to elec-... 

Roskamp reported29 a similar intramolecular Diels-Alder reaction accelerated by silica gel saturated with water. The reaction led to the ready construction of the 11-oxabicyclo [6,2,1] ring systems (Eq. 12.4). The intramolecular Diels-Alder reaction has also been investigated by Keay.30 The Diels-Alder reaction of 2,5-dimethylpyrrole derivatives with dimethyl acetylenedicarboxylate in water generated the corresponding cyclization products.31... 

By means of oxidation of the initially formed 3,4-disubstituted 5-bromo-2-bromomethylpyrrole, bromine converted 3,4-disubstituted-2-methylpyr-roles and their 5-carboxylic acids into 5-bromo-5 -bromomethyl-2,2 -dipyrrolylmethanes. Similar reaction with sulfuryl chloride led to the analogous chloro species (77MI2). Whereas treatment of 2-aroyl-l,3-dimethylpyrrole-5-acetic esters with NBS brominated the vacant ring carbon, the related oxalate ester gave the 3-bromomethyl derivative (80JMC98). 

Although the hydroxy group is a relatively poor leaving group, its base-catalyzed nucleophilic substitution by the mechanism shown in Scheme 69 accounts not only for the hydrogenolysis of the 3-hydroxymethylindoles, but also for their SN reactions with ethoxide ions, cyanide ions and with piperidine. Nucleophilic substitution on 2-hydroxymethyl-pyrroles is generally precluded by the faster formation of the bis(2-pyrrolyl)methanes, but the synthesis of 2-cyano-2-(2,5-dimethyl-3-pyrroIyl) propanes from 2,5-dimethylpyrrole, propanone and potassium cyanide probably results from an SN reaction of the cyanide ion upon the initially formed 3-pyrrolylcarbinol (81USP4248784). The formation of (294)... 

Treatment of N-substituted 2,5-dimethylpyrroles 818 with complex 813 in chloroform at 0°C gives 7//-[l,2,3>4,5]pentathiepino[6,7-r ]pyrroles 819 in moderate yields (36 0%) (Scheme 157) <2005OL5725>. Further reaction of pyrroles 819 with the same mixture at room temperature leads, in an extensive reaction cascade, to 4-alkyl-37/-di[l,2]dithiolo[4,3- 3,4-,7 pyrrole-3,5(47r)-dithiones 820 in high yield (74-85%). Compounds 818 can be converted into the tricycles 820 in a one-pot operation under unusually mild conditions (with excess of S2CI2 and DABCO). Pentathiepino[6,7-r ]pyrroles 819 were obtained directly with a nonequilibrated mixture of S2CI2 and DABCO, but in low yields (8-17%). 

SAFETY PROFILE Poison by inhalation and ingestion. A corrosive eye, skin, and mucous membrane irritant. Potentially explosive reaction with water evolves hydrogen chloride and phosphine, which then ignites. Explosive reaction with 2,6-dimethylpyridine N-oxide, dimethyl sulfoxide, ferrocene-1,1 -dicarboxylic acid, pyridine N-oxide (above 60°C), sodium -L heat. Violent reaction or ignition with BI3, carbon disulfide, 2,5-dimethyl pyrrole + dimethyl formamide, organic matter, zinc powder. Reacts with water or steam to produce heat and toxic and corrosive fumes. Incompatible with carbon disulfide, N,N-dimethyl-formamide, 2,5-dimethylpyrrole, 2,6-dimethylpyridine N-oxide, dimethylsulfoxide, ferrocene-1,1-dicarboxylic acid, water, zinc. When heated to decomposition it emits highly toxic fumes of Cl" and POx. 

N-Amimpyrroles The reagent condenses with acetonylacetone in hot acetic acid to give N-phthalimido-2,S-cliinethylpynrole (2)i which on reaction with hydrazine is split to phthalhydrazide (3) and N-amino-2,5-dimethylpyrrole (4),... 

The 2H- and 3Af-pyrrolium cations are essentially iminium ions and as such are electrophilic they play the key role in polymerisation (see 16.1.8) and reduction (16.7) of pyrroles in acid. In the reaction of pyrroles with hydroxylamine hydrochloride, which produces ring-opened 1,4-dioximes, it is probably the more reactive 37f-pyrrolium cation that is the starter. Primary amines, RNH2, can be protected, by conversion into l-R-2,5-dimethylpyrroles (16.16.1.1), recovery of the amine being by way of this reaction with hydroxylamine." ... 

OXICLORURO de FOSFORO (10025-87-3) Fumes in moist air. Contact with water, steam, or alcohols produces hydrochloric acid, phosphoric acid, and phosphine gas, which is pyrophoric, with possible ignition or explosion (may be a delayed reaction). Contact with air produces corrosive fumes. Violent reaction with carbon disulfide, 2,6-dimethylpyiidine-M-oxide, dimethyl sulfoxide, ferrocene-l,l -dicarboxylie acid, pyridine, zinc powder. Reacts, possibly -violently, with acids, alkali metals, alkalis, combustible materials, dimethyl formamide, organic matter, zinc powder. Incompatible with acetic anhydride, iV,A -dimethyl formamide, 2,5-dimethylpyrrole, sodium. Rapid corrosion of steel and most metals, except lead, occurs in the presence of moisture. 

Surprisingly, the reaction of CF2I2 with pyrrole (lb) and A -methylpyrrole (la) gave the trifluoromethylated products 38b and 38a in moderate yields under UV irradiation in DMF (Table 1, entries 5 and 6) [33]. In contrast the related reaction with 2,5-dimethylpyrrole 67 gave the trifluoromethylated dimer 68 instead of the desired 2,5-dimethyl-3-trifluoromethylpyrrole. 

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