Aldehydes by formylation

Synthesis of the remaining half of the molecule starts with the formation of the monomethyl ether (9) from orcinol (8). The carbon atom that is to serve as the bridge is introduced as an aldehyde by formylation with zinc cyanide and hydrochloric acid (10). The phenol is then protected as the acetate. Successive oxidation and treatment with thionyl chloride affords the protected acid chloride (11). Acylation of the free phenol group in 7 by means of 11 affords the ester, 12. The ester is then rearranged by an ortho-Fries reaction (catalyzed by either titanium... 

A further example of electrophilic substitution is the synthesis of pyrazole aldehydes by formylation with dimethylformamide.620,628... 

Synthesis of aromatic aldehydes by formylation of phenols, pyrroles with CHCU-base (dichlorocarbene) (see 1st edition). 

STILES-SISTI Formylation aldehydes by formylation of Grignard... 

Gattermann-Koch reaction Formylation of an aromatic hydrocarbon to yield the corresponding aldehyde by treatment with CO, HCl and AICI3 at atmospheric pressure CuCl is also required. The reaction resembles a Friedel-Crafts acylation since methanoyl chloride, HCOCl, is probably involved. 

The strategies used in the synthesis of polymethine dyes are illustrated for a series of indoline derivatives in Scheme 6.1. There is an even wider range of synthetic routes to polymethine dyes than is described here, but they are based for the most part on a similar set of principles. The starting material for the synthesis of this group of polymethine dyes is invariably 2-methylene-1,3,3-trimethylindolenine (121), known universally as Fischer s base. As illustrated in the scheme, compound 121 may be converted by formylation using phosphoryl chloride and dimethylformamide into compound 122, referred to as Fischer s aldehyde, which is also a useful starting material for this series of polymethine dyes. When compound 121 (2 mol) is heated with triethylorthoformate (1 mol) in the presence of a base such as pyridine, the symmetrical cyanine dye, C. I. Basic Red 12 109 is formed. The synthesis of some hemicyanines may be achieved by... 

A particularly interesting reaction is the C-formylation[2] of alkylidenephosphoranes by A-formylimidazole to give a-formyl derivatives (C6H5)3P=C(R)CHO which can be further transformed into a,/ -unsaturated aldehydes by Wittig reaction, or hydrolyzed to produce aldehydes RCH2-CHO. 

Formylation of an alkyl or aryl halide to the homologous aldehyde by transformation to the corresponding organometallic reagent then addition of DMF (M = Li, Mg, Na, and K). 

The behaviour of the ruthenium catalysts is quite different from that previously reported for cobalt carbonyl catalysts, which give a mixture of aldehydes and their acetals by formylation of the alkyl group of the orthoformate (19). The activity of rhodium catalysts, with and without iodide promoters,is limited to the first step of the hydrogenation to diethoxymethane and to a simple carbonylation or formylation of the ethyl groups to propionates and propionaldehyde derivatives (20). 

A recent report by Yoneda et al. describes the selective displacement of formyl hydrogen with fluorine in aliphatic aldehydes by electrolysis in base nHF (base=pyridine, Et3N n=3-6) systems, both neat and in acetonitrile and sulpholane solutions [32],e.g. 

Relatively few simple benzo[6]furan derivatives have been studied by X-ray or electron diffraction techniques. (Their hydro derivatives are better known.) An aldehyde prepared by formylating 2,4,7,-trimethylbenzo[fr]furan could not be orientated by spectroscopic methods so was converted into the derivative (36) and found to have the dimensions shown (81CSC83). In the dibenzofuran (37) (78CSC629) the effect of an acetyl group on the bond lengths and angles can be assessed by internal reference and seems to be very small, yet the molecule is nearly planar and is the s-syn rotamer in conformity with the later discussion. 

The oxidation of a-hydroxy acids by benzyltrimethylammonium tribromide (BTMAB) to the corresponding carbonyl compounds shows a substantial solvent isotope effect, A (H20)/A (D20) = 3.57, but no KIE for a-deuteromandelic acid.133 The oxidation of glucose by hypobromous acid is first order in glucose and the acid.134 [l,l-2H2]Ethanol shows a substantial kinetic isotope effect when oxidized by hexamethylenetetramine-bromine (HABR) in acetic acid to aldehyde.135 Kinetics of the oxidation of aliphatic aldehydes by hexamethylenetetramine-bromine have been studied by the same group.136 Dioxoane dibromide oxidizes y-tocopherol to 5-bromomethyl-y-tocopherylquinone, which spontaneously cyclizes to 5-formyl-y-tocopherol.137... 

Phenols are smoothly converted into phenolic aldehydes by reaction with chloroform in the presence of base (the Reimer-Tiemann reaction). This overall formylation reaction is of interest in that it involves the generation from chloroform and alkali of the reactive intermediate, dichlorocarbene (2). This effects electrophilic substitution in the reactive phenolate ions giving the benzylidene dichloride (3) which is hydrolysed by the alkaline medium to the corresponding hydroxyaldehyde. The phenolic aldehyde is isolated from the reaction medium after acidification. 

It is well known that benzophenone generates a biradical through n-ir electronic transition under irradiation ( 340 nm). Irradiation of a mixture of 1,4-benzoquinone (34) and aromatic aldehydes in the presence of benzophenone generates 2-aroyl-l,4-dihydroxybenzene (35) [47-49]. This reaction comprises of the abstraction of a formyl hydrogen atom of an aromatic aldehyde by the oxygen-centered radical of the benzophenone biradical to form an aroyl radical and a 1,1-diphenylhydroxymethyl radical, and addition of the nucleophilic aroyl radical to 1,4-benzoquinone (34) to form a phenoxyl radical derivative, which finally abstracts a hydrogen atom from an aromatic... 

Sunlight irradiation (solar photochemical synthesis) of 1,4-naphthoquinone (27) in the presence of aldehyde (28) in a mixture of -butanol and acetone gives a good yield of the corresponding acyl hydroquinone (29) through the abstraction of the formyl hydrogen atom of aldehyde by the excited triplet biradical derived from 1,4-naphthoquinone, followed by the reaction of the acyl radical with 1,4-naphthoquinone (eq. 12.7). Here,... 

Most likely, the two main pathways consist of reactions of the electrophilic ring-opened aldehyde form of the hemiacetal with bionucleophiles and of reactions of a unique multi-centered cationic nucleophile that can be generated from DIMBOA by N-O-fission.37 Recently, we reported a novel hypothesis for the mode of bioactivity based on the formation of 3-formyl-6-methoxybenzoxazolin-2(3H)-one (FMBOA) by formal dehydration of DIMBOA.40 FMBOA was proven to be a potent formyl donor towards typical nucleophiles occurring in biomolecules and could, if formed under natural conditions, also lead to biological effects by formylation of biomolecules. The mechanism of this new dehydration was elucidated with [2-13C]-DIMBOA.33... 

Fischer s aldehydes having a 2-hydroxyethyl or 2-chloroethyl substituent on the N atom and a 5-nitro substituent were prepared by formylation of the corresponding... 

Halogenated selenophene-2-aldehydes may be obtained either from selenophene-2-aldehyde halogenated (chlorinated or brominated) by the respective V-halosuccinimide72 or by formylation of the 2-halo-selenophenes.72,73... 

Oxidations of aromatic aldehydes to formyl esters of phenols and to phenols are accomplished by hydrogen peroxide [171, 172, 173] or by organic peroxy adds such as peroxyacetic acid [259], peroxybenzoic acid [302], and m-chloroperoxybenzoic acid [5/5, 318] (equations 360-363). 

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