1- Aryl-4-formyl

In each table, substituted azoles are ordered in the following way alkyl, substituted alkyl, aryl, formyl, acetyl, carboxylic acid, alkoxycarbonyl, cyano, amino, azido, diazonium salt, nitroso, nitro, hydroxy, alkoxy, fluoro, chloro, bromo, and iodo. 

After these pioneering studies, a number of other research groups reported on the cleavage of C-H bonds via the use of a stoichiometric amount of transition-metal complexes [7]. To date, several types of catalytic reactions involving C-H bond cleavage, for example, alkyl, alkenyl, aryl, formyl, and active methylene C-H bonds have been developed [8]. In many cases,for these types of catalytic reactions, ruthenium, rhodium, iridium, platinum, and palladium complexes all show catalytic activity. 

Ruthenocene has aromatic properties similar to ferrocene and its electrophilic substitution reactions are liable to proceed. For example, a Friedel-Crafts acylation, metalation, arylation, formylation, a Mannich reaction and sulfonation all readily proceed as shown in Scheme 16.2 [17]. 

Hydrazinopyridazines are easily formylated with formic acid or ethyl formate and acety-lated with acetic anhydride. A-Pyridazinylthiosemicarbazides are obtained from thiocyanates or alkyl- and aryl-isothiocyanates. Hydrazinopyridazines condense with aliphatic and aromatic aldehydes and ketones to give hydrazones. 

Isoxazole, 5-(p-anisyl)-3-phenyI-synthesis, 6, 63 Isoxazole, 4-aroyl-3,5-diaryI-synthesis, 6, 71 Isoxazole, aryl-UV spectra, 6, 4 Isoxazole, 3-aryl-5-unsubstituted ring cleavage, 6, 30 Isoxazole, 5-aryl-3-chloro-reactions, 5, 104 Isoxazole, 3-aryI-4-formyl-synthesis, 6, 84 Isoxazole, 3-aryl-5-methoxy-thermal isomerization, 6, 15 Isoxazole, 3-aryl-5-methyl-synthesis, 6, 63, 84 Isoxazole, 4-azorearrangement, 5, 719... 

Pyridazine, 4-amino-5-formyl-3,6-dimorpholino-synthesis, 3, 346 Pyridazine, 4-amino-3-halo-reaction with potassium amide, 3, 29 Pyridazine, aryl-synthesis, 3, 28 Pyridazine, arylthio-synthesis, 3, 27 Pyridazine, 3-azido-... 

Thiophene, 2-amino-3-cyano-5-phenyl-synthesis, 4, 888-889 Thiophene, 3-amino-4,5-dihydro-cycloaddition reactions, 4, 848 Thiophene, 2-amino-3-ethoxycarbonyl-ring opening, 4, 73 Thiophene, 2-amino-5-methyl-synthesis, 4, 73 Thiophene, 2-anilino-synthesis, 4, 923-924 Thiophene, aryl-synthesis, 4, 836, 914-916 Thiophene, 2-(arylamino)-3-nitro-synthesis, 4, 892 Thiophene, azido-nitrenes, 4, 818-820 reactions, 4, 818-820 thermal fragmentation, 4, 819-820 Thiophene, 3-azido-4-formyl-reactions... 

Hydroxy group of rru -7,9u-H-7-(prepared from 7-formyl-2-(2-pyrimidyl)perhydropyrido[l,2-u]pyrazine by the treatment with MeOCH2P(Ph)3Cl in the presence of -Pr2NH in THF at 0°C, than with BuLi at room temperature (99MIP6). 

While the Friedel-Crafts acylation is a general method for the preparation of aryl ketones, and of wide scope, there is no equivalently versatile reaction for the preparation of aryl aldehydes. There are various formylation procedures known, each of limited scope. In addition to the reactions outlined above, there is the Vdsmeier reaction, the Reimer-Tiemann reaction, and the Rieche formylation reaction The latter is the reaction of aromatic compounds with 1,1-dichloromethyl ether as formylating agent in the presence of a Lewis acid catalyst. This procedure has recently gained much importance. 

Functional biaryl derivatives are important industrial chemicals. They are used as monomers for the production of high performance and other polymers, as well as dyes, pharmaceuticals and agrochemical intermediates. We have developed an improved method for the dehalogeno-dimerization of aryl bromides to yield biaryl derivatives under mild conditions (temperature < 100°C, atmospheric pressure) using a common base, a 5 % Pd/C catalyst (0.1 - 10 % w/w, based on the starting material) in an aqueous medium and formyl hydrazine as the reducing agent. Several examples of biaryl derivatives are discussed. 

These catalysts are believed to function through an acyclic TS. In addition to the normal steric effects of the open TS, the facial selectivity is probably influenced by tt stacking with the aryl ring and possibly hydrogen bonding by the formyl hydrogen.152... 

Pyrazolo[4,3-e][l,2,4]triazine derivatives have been prepared from oximes of 5-aryl- and 5-formyl-l,2,4-triazines <06MI191 >. Novel pyrazolo[5,1 -c][ 1,2,4]triazines incorporating an Af-(2-oxoethyl)phthalimide moiety have been reported <06JCR(S)6>. 

Other electrophilic substitution reactions on aromatic and heteroaromatic systems are summarized in Scheme 6.143. Friedel-Crafts alkylation of N,N-dimethyl-aniline with squaric acid dichloride was accomplished by heating the two components in dichloromethane at 120 °C in the absence of a Lewis acid catalyst to provide a 23% yield of the 2-aryl-l-chlorocydobut-l-ene-3,4-dione product (Scheme 6.143 a) [281]. Hydrolysis of the monochloride provided a 2-aryl-l-hydroxycyclobut-l-ene-3,4-dione, an inhibitor of protein tyrosine phosphatases [281], Formylation of 4-chloro-3-nitrophenol with hexamethylenetetramine and trifluoroacetic acid (TFA) at 115 °C for 5 h furnished the corresponding benzaldehyde in 43% yield, which was further manipulated into a benzofuran derivative (Scheme 6.143b) [282]. 4-Chloro-5-bromo-pyrazolopyrimidine is an important intermediate in the synthesis of pyrazolopyrimi-dine derivatives showing activity against multiple kinase subfamilies (see also Scheme 6.20) and can be rapidly prepared from 4-chloropyrazolopyrimidine and N-bromosuccinimide (NBS) by microwave irradiation in acetonitrile (Scheme... 

This was later extended to the synthesis of novel pyrimido-[l,3-a]-pyrimidines under solvent-free conditions ethyl-2-armno-4-aryl-l,4-dihydro-6-phenylpyrimidine-5-car-boxylates react regioselectively with 3-formyl chromone or diethyl (ethoxymethylene) malonate, without solvent, to afford pyrimido-[l,3-a]-pyrimidines [92] (Scheme 8.66). 

A complicating feature of studies of carboxylic acid and their corresponding esters, having proximate keto or formyl groups, is the occurrence of ring-chain tautomerism, as in Scheme 1 (Valters and Flitsch, 1985). The rates of conversion of the ring and chain acids ([1] and [2] R = H) are rapid. However, both the pseudo and normal esters ([1] and [2], R = alkyl or aryl) can be isolated in favourable circumstances. The latter esters can also be interconverted by base- or acid-catalysis under suitable conditions. 

Arylphosphines in rhodium catalyzed hydroformylation reactions exchange an aryl group for an alkyl, principally linear alkyl, corresponding to the alkene being hydro-formylated to give an alkyldiarylphosphine [22](see Equation 2.5). 

Based on the use of di-l-adamantyl-n-butylphosphine (cataCXium A) 1 as ligand, a general and efficient palladium-catalyzed formylation of aryl and heteroaryl bromides has been developed by Degussa AG... 

Klaus S, Neumann H, Zapf A, Striibmg D, Hiibner S, Almena J, Riermeier T, GroB P, Sarich M, Krahnert W-R, Rossen K, Beller M (2006) A general and efficient method for the formylation of aryl and heteroaryl bromides. Angew Chem Int Ed 45 154—156... 

Aromatic compounds, 13 108-109 13 680. See also Aromatics acylation of, 12 173-181 amination of, 12 184 arylation of, 12 170-171 Cycloalkylation of, 12 169 in diesel fuel, 12 425 formylation of, 12 178 Friedel-Crafts acylation of, 12 174 Friedel-Crafts alkylation of, 12 164 nitration of, 12 182-183 oxidative coupling of, 19 654 sulfonation of, 12 181 sulfonation reagents for, 23 521-524 Aromatic-containing polymers, sulfonation of, 23 535-536... 

The base-catalysed addition of thiols to Jt-electron-deficient alkenes is an important aspect of synthetic organic chemistry. Particular use of Triton-B, in place of inorganic bases, has been made in the reaction of both aryl and alkyl thiols with 1-acyloxy-l-cyanoethene, which behaves as a formyl anion equivalent in the reaction [1], Tetra-n-butylammonium and benzyltriethylammonium fluoride also catalyse the Michael-type addition of thiols to a,P-unsaturated carbonyl compounds [2], The reaction is usually conducted under homogeneous conditions in telrahydrofuran, 1,2-dimethoxyethane, acetone, or acetonitrile, to produce the thioethers in almost quantitative yields (Table 4.22). Use has also been made of polymer-supported qua-... 

Under favourable circumstances, the initially formed /V-ylid reacts further through C-N cleavage. Thus, in the presence of a strong nucleophile, such as a phenoxide anion, the quaternary dichloromethylammonium cation forms an ion-pair with the phenoxide anion (Scheme 7.27), which decomposes to yield the alkyl aryl ether and the /V-formyl derivative of the secondary amine [22, 23]. Although no sound rationale is available, the reaction appears to be favoured by the presence of bulky groups at the 4-position of the aryl ring. In the absence of the bulky substituents, the Reimer-Tiemann reaction products are formed, either through the breakdown of the ion-pair, or by the more direct attack of dichlorocarbene upon the phenoxide anion [22,23],... 

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