Aldehyde preparation

Aqueous aza-Diels-Alder reactions of chiral aldehydes, prepared from carbohydrates and with benzylamine hydrochloride and cyclopentadiene, were promoted by lanthanide triflates (Eq. 12.65).137 The nitrogen-containing heterocyclic products were further transformed into aza sugars, which are potential inhibitors against glycoprocessing enzymes. 

These authors also found that the addition of excess MgO during the in situ preparation of allyltantalum species improved reaction outcomes, even allowing for the first example of allylation of imines derived from aliphatic amines and aliphatic aldehydes (prepared in situ at room temperature in the presence of molecular sieves) (Equation (18)). The selective addition to imines permitted three-component reactions. 

The synthesis of aldehydes via hydroformylation of alkenes is an important industrial process used to produce in the region of 6 million tonnes a year of aldehydes. These compounds are used as intermediates in the manufacture of plasticizers, soaps, detergents and pharmaceutical products [7], While the majority of aldehydes prepared from alkene hydroformylation are done so in organic solvents, some research in 1975 showed that rhodium complexes with sulfonated phosphine ligands immobilized in water were able to hydroformylate propene with virtually complete retention of rhodium in the aqueous phase [8], Since catalyst loss is a major problem in the production of bulk chemicals of this nature, the process was scaled up, culminating in the Ruhrchemie-Rhone-Poulenc process for hydroformylation of propene, initially on a 120000 tonne per year scale [9], The development of this biphasic process represents one of the major transitions since the discovery of the hydroformylation reaction. The key transitions in this field include [10] ... 

Reaction between D-Cys and an oxazoline aldehyde, prepared from l-Phe gave the bicyclic compound 83 [92H(34)903], A derivative of the same system was obtained from penicillamine with a functionalized AA (88CC1128). 

Lead tetraacetate is used as a highly selective oxidizing agent in organic synthesis. This includes oxidation of glycols into aldehydes, preparation of cyclohexyl acetate, production of oxahc acid, and in structural analysis of sugars. 

Aldehydes (Preparation of Sample). Transfer 120ml of alcohol sample to a 250ml Erlenmeyer flask, add about 20m 1 of distd w and a few grains of carborundum. Distill slowly into a 100ml volumetric flask to the mark, and mix... 

Addition of organometallic reagent to aldehyde preparation of secondary alcohols... 

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. 

As mentioned in Section 10.6.2, synthesis of 1-hydroxyethylene peptides can be initiated by adding a ferf-butoxycarbonyl N-protected a-amino aldehyde to an optically active Grignard reagent (Scheme 7)J11-13 This reaction affords a diastereomeric mixture of the C4 epimers of the hydroxy ether in good yields. In most cases the mixture is enriched in the 45-epimer and the epimers are readily separable. The yields and the ratios of the resulting 45- and 4R-epimers obtained from several examples of this reaction are summarized in Table 1. When this reaction was attempted with the aldehyde prepared from Aa,Ae-bis-tert-butoxycarbonyl-protected Lys, the desired product was not obtained. The anion of the Lys Ne-tert-butoxy-carbonylamino group probably reacts with the aldehyde to form a cyclic aminol that does not... 

The amino aldehydes Boc-Ala-H, Boc-Leu-H, Boc-Phe-H, and Boc-Thr(Bzl)-H had a much higher enantiomeric purity when prepared by reduction of Weinreb amides compared to the identical aldehydes prepared by the Collins oxidation of the alcohols (Table 5). 1314-20 ... 

Table 5 Optical Rotation of a-Amino Aldehydes Prepared by Reduction Followed by...

The formation of the y-lactams is almost perfectly diastereoselective if cyclic a-amino aldehydes or the aldehyde prepared from valine are used as starting materials. As it is shown in the following scheme, the electroreduction of the obtained optically pure y-lactams followed by the reduction with LAH yields the corresponding optically pure pyrrolizidine and indolizidine skeletons. 

Zinc-mediated addition of CF3CCI3to an aldehyde preparation of 4-methyl-2,2-dichloro-1,1,1-trifluoro-3-pentanol28... 

Preparation of b/s(5-acetoxypentyl)zinc by iodine-zinc exchange and its enantioselective addition to an aldehyde preparation of (6S)-5-bromo-6-hydroxy-l 1 -acetoxyundec-4-ene9... 

Electrochemical preparation of a functionalized benzylic zinc reagent and its coupling with a functionalized aromatic aldehyde preparation of 2-(4-cyanophenyl)-1-(4-methoxyphenyl)ethanol9... 

Conjugate addition reaction of a mixed dialkylzinc reagent to an unsaturated aldehyde preparation of ethyl (Moxomethyljdecanoate28... 

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