Aldehyde results

The search for catalyst systems which could effect the 0x0 reaction under milder conditions and produce higher yields of the desired aldehyde resulted in processes utilizing rhodium. Oxo capacity built since the mid-1970s, both in the United States and elsewhere, has largely employed tertiary phosphine-modified rhodium catalysts. For example, over 50% of the world s butyraldehyde (qv) is produced by the LP Oxo process, technology Hcensed by Union Carbide Corporation and Davy Process Technology. 

Perfluoroalkyl- and perfluoroaryltitanium compounds were prepared m situ via reaction of the corresponding Gngnard reagents with chlorotris(diethyl-amido)titanium [28S] Reaction of the titanium compounds with aldehydes resulted in fluoroalkylative amination [288] (equation 192)... 

Addition to unsaturated aldehydes results eitier in tlie 1,2 - or in tie 1,4-addition product, depending on tlie reaction conditions. Tluis, in tlie case of ciimam-aldebyde, tlie 1,2-additioii product is produced iii tlie presence of BF -OEtz and tie 1,4-addition product is obtained in tie presence of Me- SiCl (Scienie 2.46) [97]. 

The work of Harries and Himmelmann provides considerable confirmation of the individuality of the aldehydes citronellal and rhodinal. By the action of ozone on the aldehyde, results differ materially according to the source of the citronellal, and those chemists are of opinion that the two complexes—... 

Tiemann and Eeimer have prepared vanillin by the action of chloroform on guaiacol in an alkaline medium. The mixture is boiled under a reflux condenser for six hours. A mixture of vanillin and meta-methoxysalicylic aldehyde results. The mixed aldehydes are separated from the reaction mass by means of bisulphite in the usual manner, and the liberated aldehydes are separated in a current of steam. The vanillin is formed according to the following reaction—... 

Low -molecular-weight ozonides are explosive and are theretore not isolated. Instead, the ozonide is immediately treated with a reducing agent such as zinc metal in acetic acid to convert it to carbonyl compounds. The net result of the ozonolysis/reduction sequence is that the C=C bond is cleaved and oxygen becomes doubly bonded to each of the original alkene carbons. If an alkene with a letrasubstituted double bond is ozonized, two ketone fragments result if an alkene with a trisubstituted double bond is ozonized, one ketone and one aldehyde result and so on. 

Ghosh and co-workers have recently used the indanyl-derived auxiliary 69 (Table 1.9) in titanium enolate condensations with a range of aldehydes [34], Of the four possible diastereomers, only the anti 71 and syn TL were produced (the alternative anti and syn diastereomers were not detected by 1H or 13C NMR). The use of monodentate aliphatic aldehydes resulted in the formation of anti diastereomers... 

High simple, as well as induced, stereoselectivity emerge in the addition of the (Z)-enolsilane to the same aldehyde, resulting in mainly one diastcrcomer the diastereomeric ratio is 92 8 (major isomer/sum of all other diastereomers)14. 

Using optimized reaction conditions, the Wittig reactions with four of the five aldehydes resulted in an improvement in their yields (see Figure 4.89 below) [13]. 

Figure 11 Structure of the phenoxybenzoic acid (PBA) immunogen hapten. Conjugation to the protein through the aldehyde resulted in an immunogen that generated antibodies selective and sensitive for PBA...

The present homoallylation with isoprene under Ni-Et3B catalysis shows marginal success for the reaction with aliphatic aldehydes. Results are summarized in Table 6. Primary alkyl aldehydes (bearing no a-substituents) and sterically less-hindered secondary alkyl aldehydes undergo the homoallylation successfully to provide the expected products in good yields with excellent stereoselectivity (runs 1-5). The results in runs 3-5 indicate that the present reaction shows almost no diastereofacial selectivity with respect to the a-stereo centers of secondary alkyl aldehydes. Sterically demanding aldehydes, such as cyclohexanecarbaldehye and pivalaldehyde, provide the... 

Both modified cobalt and modified rhodium systems have been successfully employed. In general, both have produced good yields of linear aldehyde. Results are tabulated in Table XXVIII. 

Asymmetric reactions of a nopadiene-derived r 3-allyltitanocene complex with aldehydes have been studied [34]. In several cases, new terpenoid chirons have been prepared with de. > 95%. Reactions of the n -tiglyltitanoccne complex with a series of chiral aldehydes resulted in modest facial selectivities [35]. Complex structural effects on selectivity have been observed. 

Azomethine ylides. The reaction of 1 with the oxime of an aldehyde results in an iminium salt 2. Desilylation of 2 (CsF) gives rise to an azomethine ylide (a) that undergoes 1,3-dipolar cycloaddition with electron-deficient alkenes (equation I). 

Hydroformylation of hetero olefins such as carbonyl compounds is not known to proceed with significant levels of efficiency, whereas the hydroformylation of olefins has been developed to a sophisticated stage. Generally, aldehydes resultant from the latter process exhibit a low propensity to undergo further hydroformylation, with the exception of some activated aldehydes. The rhodium-catalyzed hydroformylation of formaldehyde is the key step in the synthesis of ethyleneglycol from synthesis gas. Chan et al. found... 

Condensation of 1-naphthol and hetaryl- or substituted-berrzaldehydes in the presence of ammonia, and subsequent acidic hydrolysis, gave 2 in moderate yields. Reactions of amino naphthols with eqrrivalent amormts of aldehydes resulted in... 

The scope was illustrated with 35 examples using various P-ketoesters as well as acetylacetone as 1,3-dicarbonyl compound. The use of aliphatic a,P-unsaturated aldehydes resulted in low yield and inferior enantioselectivity. Transformation of the DHP products into other optically active heterocyclic... 

Nitroxyl mediated electro-oxidation of primary amines also leads to formation of the imine and the further oxidation to the nitrile. In anhydrous acetonitrile containing 2,6-lutidine as a base, the nitrile is formed. In aqueous acetonitrile, hydrolysis of the imine intermediate is fast and good yields of the aldehyde result... 

Mercaptoacids were successfully applied in the MRCs with aminozoles on the way to the novel sulfur containing seven-membered heterocycles [145-147], Thus, condensation of 5-aminopyrazoles with mercaptoacetoacid and aromatic ketones or aldehydes resulted in the formation of pyrazolothiazepines 107 (Scheme 50). 

Condensahon of N-tritylglycin with donor or acceptor subshtuted aldehydes results in fulleropyrrolidines whose amino functionality can be easily deprotected with triflic acid and further funchonalized with, e.g., another donor [236]. Thus, access to various triads is provided. An example for a donor-acceptor-donor triad is given in Scheme 4.38. 

The Lewis acid-mediated reactions of 2-aza-l,3-dienes and aldehydes, resulting in tetrahydro-l,3-oxazin-4-one derivatives, were explained in terms of the competitive existence of two reaction pathways a [4+2] hetero-Diels-Alder cycloaddition reaction and a Mukaiyama aldol reaction <2001TA439>. 

The ring closures of l,4-diaminobutane-2,3-diols or 2,3-diaminobutane-l,4-diols with aldehydes resulted in formation of fused bis(tetrahydro-l,3-oxazine) heterocycles, diastereomeric l,5-dioxa-3,7-diazadecalins and l,5-diaza-3,7-dioxadecalins, as main products <1997TL3573, 1999EJO2033, 1999JOC1166, 2001EJ0729>. As in the case of the N-substituted... 

Reactions of lithium and titanium compounds 2, generated in situ by deprotonation of alkynylsilanes with tm-butyllithium, followed by addition of titanium(IV) isopropoxide and an aldehyde result either in a-hydroxyallenes without axial dissymmetry or in /J-hydroxyalkyn-es90 91. 

The reaction of 2-(l-alkyl-2-alkenyl)-l,3,2-dioxaborolancs with a suitably chosen aldehyde resulting in further C—C bond formation with chirality transfer is described in Section D.1.3.3.3.3. A number of analogous reactions of chiral allylboronic esters with aldehydes are described there as well. 

In contrast to wild-type BFD, BAL accepts aromatic aldehydes substituted in the ortho position as well. Only a few aromatic aldehydes, such as pyridine 3- and 4-carbaldehyde as well as sterically exceedingly demanding aldehydes, resulted either in very low yields or in no benzoin condensation at all [62]. Moreover, mono- and dimethoxyacetaldehyde are good substrates for BAL, leading to highly functionalized enantiopure hydroxypropiophenone derivatives (Scheme 2.2.7.22) [63]. 

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