O-alkyl aromatic aldehyde

Keywords o-alkyl aromatic aldehyde, photocyclization, benzocyclobutanol... 

The first clue to the existence of the SrnI mechanism came from product studies both in aliphatic and aromatic cases. It was noticed that in the reaction of benzyl and substituted benzyl chlorides with the 2-nitropropane anion, oxygen alkylation, yielding the oxime and then the aldehyde, occurs exclusively in the case of benzyl chloride and 3-nitrobenzyl chloride, whereas, with 4-nitrobenzyl chloride, the yield of aldehyde is only 6% and the carbon-alkylated (104) product is obtained in 92% yield (Kornblum, 1975). This was interpreted as the result of a competition between 8, 2 (O-alkylation) and S l (C-alkylation) reactions. In the aromatic case, it was observed that the reaction of 5- and 6-halopseudocumenes with KNHj in liquid ammonia (Kim and Bunnett, 1970) forms the 5- and 6-pseudocumi-dines in a ratio which is the same whether the starting compound is the 5- or 6-isomer in the case of the chloro- and bromo-derivatives, as expected from an aryne mechanism (Scheme 9), whereas much more non-rearranged... 

O-dealkylation. Aromatic methyl and ethyl ethers may be metabolized to give the phenol and corresponding aldehyde (Fig. 4.16), as illustrated by the de-ethylation of phenacetin (Fig. 4.20). Ethers with longer alkyl chains are less readily O-dealkylated, the preferred route being co-l-hydroxylation. 

The HO-toluene adduct corresponds to the methyl-substituted o-, m- and p-hydroxycyclohexadienyl radical isomers. The kinetics of formation and of unimolecular dissociation of HO-aromatic adducts have been studied extensively [30], The benzyl radical -CH2 is converted to the aldehydic product 0-CHO in the presence of NO via a series of reactions analogous to those involving simple alkyl radicals. Bandow et al. [144-146] have determined the yields of aromatic aldehydes to be < 12% of the overall reactions of toluene, xylenes, and trimethylbenzenes, and thus, the H-atom abstraction channel is relatively small but significant. In the case of 0-CHO, the... 

Dai and co-workers [183] have reported a one-pot U-4CR followed by an intramolecular O-alkylation sequence starting from a 2-aminophenol in combination with an a-bromoalkanoic acid, an aromatic aldehyde and an isocyanide under controlled microwave irradiation. The U-4CR was carried out in MeOH and the resulting acyclic intermediate 131 was turned into the 3,4-dihydro-3-oxo-2/f-1,4-benzoxazines 132, without isolation, upon treatment with an aqueous solution of K2CO3 to promote the intramolecular 0-aUcylation in high yields (Scheme 102). 

Aromatic aldehyde R = alkyl, O-alkyl, OH Aromatic aldehyde... 

Condensation of o-phenylenediamine with methylglyoxal, aldohexoses and aryl or alkyl acyloins gave the corresponding quinoxalines 76. Indoloquinoxalines were obtained from isatin. Carbethoxymethylation of isatin and then reaction with o-phenylenedimine gave the respective indoloquinoxalines 77, whereas hydrazide was condensed with aromatic aldehydes and monosaccharides. L-Ascorbic acid or D-isoascorbic acid were oxidized with iodine and then reacted with o-phenylenediamine and phenylhydrazine to give quinoxalinones 78, which were cyclized to pyrazolyl-quinazolinones . ... 

A third dimension of diversity in the generation of hydantoins can be introduced as shown in Scheme 3. After coupling of an Fmoc-amino acid to Wang resin and N-deprotection to give 7, a reductive alkylation sequence using aromatic aldehydes was performed (8) before the coupling of an isocyanate (9, X = O). The cleavage... 

Condensation of salicylaldehyde and its derivatives with a variety of esters of chloroacetic acids in the presence of TBAB led to the synthesis of benzo[b]furans by means of a solid-liquid PTC reaction under the action of microwave irradiation [39]. This was a modification of one of the most popular routes to substituted benzo[b]furans, i.e. O-alkylation of O-hydroxylated aromatic carbonyl compounds with a-halogenated carbonyl compounds then intramolecular condensation. The mixture of aldehydes and chloroacetic acid esters were absorbed on potassium carbonate then irradiated in an open vessel in a domestic MW oven for 8-10 min (Eq. 26). 

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