Synthesis aldehydes from halides

SOMMELET Aldehyde synthesis Aldehyde synthesis from primary alkyl halides with hexamethylene tetramine. 

The availability of amino-substituted furazans, both by direct synthesis from aminogly-oximes and via Hofmann degradation of the corresponding carboxamides, allows urea, thiourea, imino and acylamido derivatives, for example, to be prepared by reaction with isocyanates, isothiocyanates, aldehydes and acyl halides, respectively (73JPR791, 77JCS(P1)1616). Alkoxy and acyloxy derivatives are likewise formed from hydroxyfurazans (79JHC689). 

Addition tube, 20, 21 Alanine, /3-(3,4-dihydroxyphenyl)-N-METHYL-, 22, 89, 91 Alcoholic hydrochloric acid, 22, 77, 83 standardization, 22, 80 Alcoholysis, 20, 67 Aldehyde synthesis, 20, 14 from acid chlorides by Rosenmund reaction, 21, 84, 87, 88, 110 Alkylation of thiourea, 22, 59 Alkylchlororesorcinols, 20, 59 Alkylene bromide, 20, 24 S-Alkylthiuronium halides, 22, 60 dl-ALLOTHREONINE, 20, 10 ... 

By far the most important method of preparing alcohols is the Grignard synthesis. This is an example of the second approach, since it leads to the formation of carbon-carbon bonds. In the laboratory a chemist is chiefly concerned with preparing the more complicated alcohols that he cannot buy these are prepared by the Grignard synthesis from rather simple starting materials. The alkyl halides from which the Grignard reagents are made, as well as the aldehydes and ketones themselves, are most conveniently prepared from alcohols thus the method ultimately involves the synthesis of alcohols from less complicated alcohols. 

Pinacol formation from carbonyl compounds promoted by Smij continues to interest chemists. In the presence of methyl chloroformate the products are cyclic carbonates. In a cyclitol synthesis the diastereoselectivity for cyclization is found to be dependent on the a-substituents of the aldehyde groups. Lithium halides (chloride, bromide) have a profound effect on the reactivity of Sml2 and the pinacol coupling is favored. The reduction and pinacol coupling of ketones in THF is accelerated by MejSiCl (reaction time from hours reduced to a few minutes)." ... 

Aldehyde synthesis.2 The carbanion generated from this reagent (1) reacts with an alkyl halide to give an aldehyde dimethyl mercaptal S-oxide (2). This product is easily... 

This zinc-promoted reaction has been used with a variety of carbonyl compounds. Thus, the Luche conditions were applied in a synthesis of (-1-)-muscarine using an aldehyde derived from ethyl lactate [109]. Allyl halide condensation onto a-ketoamides of proline benzyl ester gave good diastereoselec-tivity when performed in the presence of zinc dust and pyridinium p-toluene-sulfonate in a water/THF mixture. In this way, a-hydroxy ketones were obtained with good enantioselectivity after removal of the chiral auxiliary [110]. Reactions of allyl bromide under the Luche conditions with y-aldo esters afforded y-hydroxy esters, which were converted in a one-pot reaction to y-allyl-y-butyro-lactones (Scheme 22) [111]. 

It is important to distinguish this synthesis from the alkylation of a 1,3-dicarbonyl enolate with a 2-halo-ketone, with displacement of halide, producing a 1,4-dicarbonyl unit for subsequent ring closure " presumably the difference lies in the greater reactivity of the carbonyl group (aldehyde in the example) in the Feist-Benary sequence. 

B E N A R Y Conjugated Aldehyde Synthesis Formation of polyunsaturated aldehydes from vinyl halides and enaminoaldehydes (see 1st edition). 

Isoquinoline synthesis from aromatic aldehydes or benzyl halides and aminoacetal (Pomeranz-Fritsch) or from benzylamines and glyoxal acetal (Schlitter-Muller) (see 1st edition). 

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