Primary aldehydes

AW-Dimethyl-Ot-isocyanoacetamide 10 is the substrate of choice in the reaction with acetaldehyde (98.6% ee) or primary aldehydes such as propionaldehyde (96.3% ee) or isovaler-aldehyde (97.3% ee) (Scheme 8B1.5, Table 8B1.5) [19]. The oxazolinecarboxamides 11 thus prepared can be converted to P-hydroxy-a-amino acids by acidic hydrolysis. The aldol reaction... 

The primary aldehyde product is reduced to the desired butanol, or it is subjected to a base-catalyzed aldol condensation and then hydrogenated to give 2-ethylhexanol. The phthalic ester of the latter is used as a plasticiser in PVC. The first process was based on a Co2(CO)s catalyst, a precursor of HCo(CO)4. The pressure is high, ca. 200-300 bar, in order to maintain the catalyst s stability. In the 60s Shell developed a process using phosphine ligands which allowed the use of lower pressures. The catalyst is less active but it directly produces alcohols with a somewhat higher linearity. 

Bronsted base [the lithium binaphthoxides] and of a Lewis acid [La(UI)] sitting side by side at the heart of the LLB multifunctional catalyst evokes the active site of aldolases and probably explains why simple unmodified ketones and primary aldehydes can be used504. The examples in Scheme 132 illustrate the performance of this system612. 

Direct methods mentioned above are generally only practicable with tertiary aldehydes. In the case of secondary and primary aldehydes ee values achieved are still too low. Nevertheless, direct methods are important supplementary alternatives to the Mukaiyama-type reactions. 

Enantioselective synthesis of primary amines Chiral -substituted primary amines (3) can be prepared in 95% ee from SAMP hydrazones (2) of primary aldehydes (equation I). 

Template-assisted condensations of amines with formaldehyde yield a wide variety of macrocyclic products. Sepul-chrates (7) can be synthesized from the template-assisted condensation of [Co(en)3] + with formaldehyde and ammonia under basic conditions. Primary aldehydes other than formaldehyde have also been used. Caged metal ion complexes in which the metal ion is used as a template are normally... 

Example 6.5. Olefin hydroformylation with phosphine-substituted cobalt hydrocarbonyl catalyst [30], The pathway 6.9 of olefin hydroformylation with the "oxo" catalyst, HCo(CO)4, has been shown in Example 6.2 in Section 6.3. For phosphine-substituted catalysts, HCo(CO)3Ph (Ph = organic phosphine), the pathway olefin — aldehyde is essentially the same. However, these catalysts also promote hydrogenation of aldehyde to alcohol (Examples 7.3 and 7.4) and of olefin to paraffin (Example 7.5). Moreover, straight-chain primary aldehydes under the conditions of the reaction undergo to some extent condensation to aldol, which is subsequently dehydrated and hydrogenated to yield an alcohol of twice the carbon number (e.g., 2-ethyl hexanol from n-butanal see Section 11.2). The entire reaction system is... 

In the cobalt-catalyzed photochemical carbonylation of olefins, hydroformyla-tion can be performed easily at ambient temperature (and high pressure) with high primary aldehyde selectivities (cf. Section 2.1.1) [59]. Under comparable conditions allylic amines are carbonylated to 2-pyrrolidinone, Al,/V -diallylurea, and A -allyl-3-butenamide [60]. Photochemical methoxycarbonylation of olefins is possible at ambient conditions, i.e., at room temperature and atmospheric pressure [61]. 

The primary aldehyde product is reduced to the desired butanol, or it is subjected to a base-catalysed aldol condensation and then hydrogenated to give 2-ethylhexanol. The phthalic ester of the latter is used as a plasticiser in PVC. The... 

In some cases subsequent reactions of the primary aldehyde function with other functions already present in the substrate are observed, such as hemiacetal formation in hydroformylation of methallyl alcohol16 (Table 7). 

Telechem Primary amine Primary aldehyde Oligonucleotides and PCR products Amino-modified oligonucleotides and PCR products, or proteins www.arrayit.com... 

Pro-azaphosphatranes lb. Id, and 9b catalyze the reaction of aldehydes with acetonitrile to give the title compounds in very good to excellent yields [124]. In a comparison of the efficacy of le with Id in several cases, le was more effective but If was quite inactive [71]. Aldehydes taking part in this reaction form secondary alcohols which are less sterically hindered and can be more easily depro-tonated, thus leading to a,jS-unsaturated nitriles. Primary aldehydes, however, undergo aldol condensation. 

The urea-formaldehydes (UFs) are the most important and most used class of amino resin adhesives. Amino resins are polymeric condensation products of the reaction of aldehydes with compounds carrying aminic or amidic groups. Formaldehyde is by far the primary aldehyde used. The advantage of UF adhesives are their (1) initial water solubility (this renders them eminently suitable for bulk and relatively inexpensive production), (2) hardness, (3) nonflammability, (4) good thermal properties, (5) absence of color in cured polymers, and (6) easy adaptability to a variety of curing conditions [1,2]. 

For a general introduction, see Wood adhesives - basics. Aminoplastic resins are polycondensation products of the reaction of aldehydes with compounds carrying amine or amide groups. Formaldehyde is by far the primary aldehyde used. The name amino-plastic is traditional, but is a misnomer these are thermosetting, irreversibly hardening resins. Two main classes of these resins exist urea-formaldehyde (UF) resins and melamine-formaldehyde (MF) resins. Today, for wood adhesives, pure MF resins are not used anymore because of cost, and only melamine-urea-formaldehyde (MUF) adhesives are used. The main use of these resins is in composite products such as particle board, plywood, medium density fibreboard (MDF), oriented strand board (OSB), glu-lam/flngerjointing and furniture. 

Although acetaldehyde is the primary aldehyde present in wines, there are reports of hydroxymethylfurfural, furfural, and higher aldehydes. Acetal and acetone are also found in some wines. 

Scheme 9.39. Two idealized representations of the reaction between the Grignard reagent, methyhnagnesium iodide (CHsMgl), and methanal (formaldehyde, H2C=0) followed by hydrolysis. In both, the primary aldehyde is converted to a primary alcohol. The difference is in the molecularity of the Grignard reagent.

It may be interesting and useful to note that prenylation of aldehyde is quite chemose-lective while prenylation of primary aldehydes proceeds very smoothly, no reaction takes place with secondary and tertiary aldehydes as shown in Table IX. 

Crabtree and Rheingold [13, 14] found that a cationic catalyst generated from [RhCl(NBD)]2 (NBD = norbornadiene) and triphos in the presence of CO or formaldehyde could decarbonylate primary aldehydes (Scheme 8.5). A mechanism was established with a hydrido-acyl complex as key component. 

Another catal)4ic asymmetric aldol reaction is shown in eq 4. Slow addition of the aldehyde is again necessary for high selectivity. Catalyst A is preferred in reactions with aromatic and unsaturated aldehydes, while catalyst B is employed in reactions with primary aldehydes. In contrast to the catalysts mentioned above (eqs 1-3), both A and B give anti aldols as the predominant... 

B. Ketones and Aldehydes Ketones and aldehydes are denoted by the carbonyl group code, (=0), associated with a secondary (ketone) or primary (aldehyde) carbon of the skeleton (e.g. 3(=0)). 

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