3,7-Diaryl- pyridines

Fused pyridines. 1-Ethynylcyclopentanol added dropwise with stirring to a mixture of acetyl chloride and a little ZnCl2 and POCI3 at 0° (exothermic to 35-40°), cooled to 20°, stirred for 1 h, and the mixture poured into 23% aq. NH4OH at 0° - 2-methyl-3,4-cyclopentenopyridine. Y 55% (85-93% with acetyl bromide or iodide). F.e.s. F.A. Selimov et al., Izv. Akad. Nauk SSSR Ser. Khim. 1988, 2604-7 2,4-dialkyl-, 2,3,4-trialkyl-, and 2,4-diaryl-pyridines (without POCI3), also 2,3,4,6-tetra-subst. pyridines from 1,3-enynes, s. ibid. 2600-4. 

In 2005, Ackermann [23a] reported the diraylation of 2-phenylpyridine using a Ru-(adamantyl)2P(0)H catalyst (Scheme 4.4). The diarylated pyridine was obtained with a yield of >98% in NMP (A/ -methylpyrrolidone), but dropped to 61% when water was used as cosolvent (33%). It should be noted that currently several industrial processes are being used where aqueous phase organometallic-catalysis is used. 

Extension to the use of acrylates afforded the desired olefination products as a mixture of the desired alkene and intra-molecnlar alkoxy-Michael addition products in high ee. Analogous methodology has been extended to the asymmetric intra-molecular lactonization of diphenylacetic acids toward benzofuranones as well as the enantioselective iodination of diaryl pyridines and methylamines. Asymmetric C—H activation of cyclopropanes has also been reported. ... 

Palladium-catalyzed Arylation of Pyridine N-Oxides and N-Iminopyridinium Ylides. Tri-tert-butylphosphine has been used in the palladium-catalyzed C-arylation of pyridine 7/-oxides and derivatives. Using palladium acetate as the catalyst, tri-tert-butylphosphine as the ligand, and 3-bromopyridine as the electrophile, the C-H arylation of pyridine tV-oxide was accomplished, yielding the 2-arylated compound as the major product and the 2,6-diarylated pyridine as a minor product (eq 24). ... 

Reaction of 2-(arylmethyleneamino)pyridines 335 and styrenes in the presence of hydroquinone afforded 2,4-diaryl-3,4-dihydro-2/f-pyrido[l,2-n]pyrimidines 336 by means of an inverse electron demand Diels-Alder reaction (95MI10). Reaction of 2-(benzylideneamino)pyridines 337 and chloroacetyl chloride gave 2-aryl-4//-pyrido[l,2-n]pyrimidin-4-ones 338 (97JMC2266). 

In aqueous pyridine solution, most diaryl sulphoxides may be oxidized to the corresponding sulphones with (dichloroiodo)benzene in reasonable yields103. The reaction involves nucleophilic attack by the sulphoxide on the electrophilic chlorine-containing species, yielding an intermediate chlorosulphonium ion which then reacts with water producing the sulphone. If the sulphoxide is optically active, then an optically active sulphone is produced in excellent optical yield when the reaction is carried out in oxygen-18 labelled water104, as indicated in equation (33). 

Wahrend N,N -disubstituierte Harnstoffe von Lithiumalanat nicht angegriffen werden, erhalt man mit Natriumboranat in siedendem Pyridin mit mittleren Ausbeuten die entsprechenden N,N -disubstituierten Formamidine. N,N -Dialkyl-harnstoffe liefern die besten Ausbeuten, N,N -Diaryl-harnstoffe die schlechtesten3. 

Diaryl-2-aminopyrimidines react with acrylonitrile in pyridine under reflux to give, after work-up, the 6,8-diaryl-2,3-dihydro-4-oxo-47/-pyrimido[l,2- ]pyrimidines in low yield <1996IJB915>. 

The following syntheses all proceeded regioselectively 4,6-diaryl-3,4-dihydropyrimidine-2-thiones with 3-bromopropionic acid in a Ac20/AcOH system <2001MI407, 2000IJH49>, or with acrylonitrile in pyridine followed by hydrolysis <1996IJB915> resulted 6,8-diaryl-2,3-dihydro+//,6//-pyrirnido[2,l+][l,3]thiazin-4-ones in good yield 4-phenyl-5-carbethoxy-3,4-dihydropyrimidine-2-thiones with benzylidenemalonitrile in a NaOAc/AcOH system... 

The ring expansion reaction of diaryl cyclopropenones and cyclopropene thiones occurring with pyridinium, sulfonium, and phosphonium enolate betaine 427268-270) is related to 1,3-dipolar cycloadditions. This process results in formation of 2-pyrones 428 by loss of pyridine (or sulfide or phosphine) and insertion of the remaining fragment C=C-0 to the C1(2)/C3 bond of the cyclopropenone ... 

The reaction of the trichloromethylarenes 146 with thiosemicarbazide 138 in a boiling methanol-pyridine mixture afforded the 2-amino-5-aryl-l,3,4-thiadiazoles, while under similar conditions trichloromethylarenes 146 were converted to the diaryl-1,3,4-thiadiazoles with thiobenzhydrazide 147 (Equation 52, Table 7) <1996RCB1185>. 

Loran and Williams, 1977. The reference intermolecular reaction is the attack of pyridine on methyl o-nitrophenyl phosphate (Kirby and Younas, 1970). Corrections for the conversion to a diaryl ester and a p-nitrophenyl leaving group are assumed to cancel out. Temperature correction uses E, = 14.8 kcal mol-1, as measured for the reference reaction 4 Lazarus et al., 1980... 

Diaryl tellurium diiodides afford the iodocyclization of 4-pentenoic acid after 5 and 4 days reflux in CHCI3 in the presence of pyridine. ... 

Typical procedure A solution of 4-pentenoic acid (0.0500 g, 0.500 mmol), bis(p-chlorophenyl)tellurium diiodide (0.302 g, 0.500 mmol) and pyridine (0.040 g, 0.500 mmol) was heated at reflux in 20 mL of chloroform for 5 days. The reaction mixture was concentrated in vacuo, and the residue was purified via chromatography on silica gel eluted with 1 1 hexane/ethyl acetate to give 0.073 g (66%) of the iodolactone and 0.140 mg (80%) of diaryl telluride. 

A peri-fused system can be synthesized by diaryl copper-catalyzed ether coupling accomplished utilizing (CuOTf)2 PhMe in pyridine (Equation (21) (2004JOC4527)). This protocol produces several annulated ring systems and gives... 

An unusual seven-membered diazaphosphatetrathia heterocycle (190) containing a chain of four sulfur atoms was obtained using diaryl or dialkyl phenyl phosphonamide 187 with sulfur monochloride in the presence of pyridine base (1993CC1684). A mechanism of the formation of 190 remains unclear but 190 was possibly formed via expected disulfide 188 which might be in equilibrium with bis(thionitroxide) 189 and the latter, in turn, could then further react with S2CI2 (Scheme 94). The extension sulfur chain was explained by the S2CI2 addition and... 

The reaction of arylacetamides with ethyl phenylpropiolate gives 4,5-diaryl-l,5-dihydro-2//,67/-pyridine-2,6-diones (197). - It has been suggested that the pyridinediones in these reactions are formed through the initial addition of either the amide anion (195) or the carbanion (196), generated under basic conditions, to ethyl phenylpropiolate (Scheme 30). 

Dichloropyridine-4-carboxaldehyde reacts with thiophenol to produce a diaryl sulfide. The diaryl compound and methyl thioglycolate undergo an aldol-type cyclization reaction in the presence of a weak base to afford 4-substituted thieno[2,3-f]pyridine derivative 121 (Scheme 38) <2002JOC943>. 

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