Halogeno-aldehydes

For convenience, the intermediate is depicted here as a spirocyclic ammonium salt, but it should be noted that such an intermediate has only been rigorously established in the vincadifformine synthesis using a-substituted <5-halogeno-aldehydes in other cases, an alternative mechanism may operate (see p. 223). 

Addition of halogens to enol acetates of aldehydes and ketones for preparation of <%-halogeno aldehydes and ketones is described on page 187. 

The Reformatsky Reaction consists of the interaction of an ester of an a-halogeno-acid with an aldehyde, a ketone or another ester in the presence of zinc. For example, if a mixture of ethyl bromoacetate and benzaldehyde is heated with zinc, the latter undoubtedly first combines with the ethyl bromoacetate to form a Grignard-like reagent (reaction A), which then adds on to the benzaldehyde Just as a Grignard reagent would do (reaction B). The complex so formed, on acidification gives ethyl p-phenyl-p-hydroxy-propionate (reaction C). Note that reaction A could not satisfactorily be carried out using... 

Almost insoluble in cold water. Higher alcohols (including benzyl alcohol), higher phenols (e.g., naphthols), metaformaldehyde, paraldehyde, aromatic aldehydes, higher ketones (including acetophenone), aromatic acids, most esters, ethers, oxamide and domatic amides, sulphonamides, aromatic imides, aromatic nitriles, aromatic acid anhydrides, aromatic acid chlorides, sulphonyl chlorides, starch, aromatic amines, anilides, tyrosine, cystine, nitrocompounds, uric acid, halogeno-hydrocarbons, hydrocarbons. 

Precursor y-halogeno alcohols are frequently prepared by the classic sequence of addition of hydrogen halide to a,/3-unsaturated aldehydes, ketones, acids or esters, followed by Grignard reaction or hydride reduction. Recently a novel and general synthesis of 3-methoxyoxetanes from 3-phenylseleno-2-propenal was reported. This method comprises a sequence of Grignard addition to the aldehyde function, treatment with two equivalents of MCPBA, and then reaction with methanolic sodium hydroxide (equation 78) (80JOC4063). 

In a continuation of an investigation of the chemistry of P-halogeno ylids, P-fluoro ylids (29) have been shown to react with aldehydes and ketones to form 2-fluoro-l,2X -oxaphosphetans (30) which rearrange to alkylphosphonates (31). The pentaco-ordinated phosphorus compounds ( 8 P= -41.6/-56.0) were also characterised by and n.m.r. 

Benzo[c] cinnoline aldehydes are as yet unknown. The 2- and 3-acetyl derivatives have been prepared, but the majority of known compounds relevant to this section are mono- and dicarboxylic acid derivatives. These include the 2-, - - 3-, ° and 4. - o2.J55,i57 monoacids and esters, the lactone of 10-hydroxybenzo[c]cinnoline-l-carboxylic acid, some halogeno- and methyl-substituted 2- and 4. carboxylic acids, and the 2,9-, 3,8-, - - and 4,7- dicarboxylic acids and derivatives. These compounds have been obtained by ring synthesis, or, in the case of 2-methylbenzo[c]dnnoline-9-carboxylic acid, by side-chain oxidation, " rather than by the introduction of substituents into benzo[c] cinnoline. Benzo[c]cinnoline-l-carbonitrile has been prepared, albeit in low... 

The weU-known synthesis from 3-halogeno-a, -imsaturated aldehydes 1 and ammonium thiocyanate, via intermediate 2, is very useful for the preparation of substituted isothiazoles 3 and for fused analogues (Scheme 1, Method A) [1,2]. 

Fluorosilicone Ketones, aldehydes, halogeno compounds, steroids, alkanoids 250... 

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