Alkenes aromatic aldehydes

Peroxomonosulfuric acid oxidi2es cyanide to cyanate, chloride to chlorine, and sulfide to sulfate (60). It readily oxidi2es carboxyflc acids, alcohols, alkenes, ketones, aromatic aldehydes, phenols, and hydroquiaone (61). Peroxomonosulfuric acid hydroly2es rapidly at pH <2 to hydrogen peroxide and sulfuric acid. It is usually made and used ia the form of Caro s acid. 

The use of Lewis acid catalysts greatly expands the synthetic utility of the carbonyl-ene reaction. Aromatic aldehydes and acrolein undergo the ene reaction with activated alkenes such as enol ethers in the presence of Yb(fod)3.35 Sc(03SCF3)3 has also been used to catalyze carbonyl-ene reactions.36... 

Dipolar addition to nitroalkenes provides a useful strategy for synthesis of various heterocycles. The [3+2] reaction of azomethine ylides and alkenes is one of the most useful methods for the preparation of pyrolines. Stereocontrolled synthesis of highly substituted proline esters via [3+2] cycloaddition between IV-methylated azomethine ylides and nitroalkenes has been reported.147 The stereochemistry of 1,3-dipolar cycloaddition of azomethine ylides derived from aromatic aldehydes and L-proline alkyl esters with various nitroalkenes has been reported. Cyclic and acyclic nitroalkenes add to the anti form of the ylide in a highly regioselective manner to give pyrrolizidine derivatives.148... 

The 3-oxo-2-pyrazolidinium ylides 315, easily available by reaction of the corresponding pyrazolidin-3-one with aromatic aldehydes, function as 1,3-dipoles in cycloaddition reactions with suitable alkenes and alkynes to provide the corresponding products. When unsymmetrical alkynes are used, mixtures of both possible products 316 and 317 are usually obtained (Equation 45). The regioselectivity of cycloadditions of the reaction with methyl propiolate is influenced by the substituents on the aryl residue using several 2,6-di- and 2,4,6-trisubstituted phenyl derivatives only compound 316 is formed <2001HCA146>. Analogous reactions of 3-thioxo-l,2-pyrazolidinium ylides have also been described <1994H(38)2171>. 

The reaction, formally speaking a [3 + 2] cycloaddition between the aldehyde and a ketocarbene, resembles the dihydrofuran formation from 57 a or similar a-diazoketones and alkenes (see Sect. 2.3.1). For that reaction type, 2-diazo-l,3-dicarbonyl compounds and ethyl diazopyruvate 56 were found to be suited equally well. This similarity pertains also to the reactivity towards carbonyl functions 1,3-dioxole-4-carboxylates are also obtained by copper chelate catalyzed decomposition of 56 in the presence of aliphatic and aromatic aldehydes as well as enolizable ketones 276). No such products were reported for the catalyzed decomposition of ethyl diazoacetate in the presence of the same ketones 271,272). The reasons for the different reactivity of ethoxycarbonylcarbene and a-ketocarbenes (or the respective metal carbenes) have only been speculated upon so far 276). 

Electrophilic substitution of the ring hydrogen atom in 1,3,4-oxadiazoles is uncommon. In contrast, several reactions of electrophiles with C-linked substituents of 1,3,4-oxadiazole have been reported. 2,5-Diaryl-l,3,4-oxadiazoles are bromi-nated and nitrated on aryl substituents. Oxidation of 2,5-ditolyl-l,3,4-oxadiazole afforded the corresponding dialdehydes or dicarboxylic acids. 2-Methyl-5-phenyl-l,3,4-oxadiazole treated with butyllithium and then with isoamyl nitrite yielded the oxime of 5-phenyl-l,3,4-oxadiazol-2-carbaldehyde. 2-Chloromethyl-5-phenyl-l,3,4-oxadiazole under the action of sulfur and methyl iodide followed by amines affords the respective thioamides. 2-Chloromethyl-5-methyl-l,3,4-oxadia-zole and triethyl phosphite gave a product, which underwent a Wittig reation with aromatic aldehydes to form alkenes. Alkyl l,3,4-oxadiazole-2-carboxylates undergo typical reactions with ammonia, amines, and hydrazines to afford amides or hydrazides. It has been shown that 5-amino-l,3,4-oxadiazole-2-carboxylic acids and their esters decarboxylate. 

The Bulfington group [17] at Johnson and Johnson Pharmaceutical have also developed a very efficient and concise synthesis (Scheme 5) of the Furst-ner intermediate (6) to lukianol A. The synthesis relies on the condensation of benzyl nitriles with aromatic aldehydes under basic conditions to give the corresponding electron deficient alkenes (23). 

Boron-Wittig reaction (12, 12-13). The direct reaction of the anion of an alkyldimesitylborane at -78° with an aromatic aldehyde followed by oxidation results in an (E)-alkene in low yield. The intermediate adduct can be isolated in about 80% yield as the silyl ether of a iyn-l,2-diol by addition of CISi(CH,), to the reaction, and this product on desilylation (HF, CHjCN) affords (E)-alkenes with high selectivity. Somewhat lower (E)-selectivity obtains in a one-pot reaction. In contrast, addition of trifluoroacetic anhydride (slight excess) to the reaction at -78° to -110° results in a (Z)-alkene with almost comparable selectivity (Z/E 9 1). 

Among those phosphonates used successfully in alkene synthesis with aromatic aldehydes were (114),106 (115),107 (116),108(117),109 and(118).110 The stereochemical... 

Behavioral observations of male white-tailed deer indicate that urine could play a role in olfactory communication in this animal [131]. To extend the knowledge of the urinary volatiles of the white-tailed deer and to investigate the possibility that vaginal mucus could also carry semiochemical information, Jemiolo et al. [132] studied the qualitative and concentration changes in the profiles of the volatiles present in these excretions. Forty-four volatiles were found in the mucus and 63 in female urine. The volatiles common to both vaginal mucus and urine included alcohols, aldehydes, furans, ketones, alkanes, and alkenes. Aromatic hydrocarbons were found only in the mucus, whereas pyrans, amines, esters and phenols were found only in the urine. Both estrous mucus and estrous urine could be identified by the presence of specific compounds that were not present in mid-cycle samples. Numerous compounds exhibited dependency on ovarian hormones. 

Reduction of aromatic aldehydes to pinacols using sodium amalgam is quite rare. Equally rare is conversion of aromatic aldehydes to alkenes formed by deoxygenation and coupling and accomplished by treatment of the aldehyde with a reagent obtained by reduction of titanium trichloride with lithium in dimethoxyethane. Benzaldehyde thus afforded /ra/is-stilbene in 97% yield [206, 209]. 

After extensive screening of various aldehydes to optimize the reaction conditions, it was found that aromatic aldehydes were able to serve as a carbon monoxide source, in which the electronic nature of the aldehydes is responsible for their ability to transfer CO efficiently [24]. Consequently, aldehydes bearing electron-withdrawing substituents are more effective than those bearing electron-donating substituents, with pentafluoro-benzaldehyde providing optimal reactivity. Interestingly, for all substrates tested the reaction is void of any complications from hydroacylation of either the alkene or alkyne of the enyne. Iridium and ruthenium complexes, which are known to decarboxylate aldehydes and catalyze the PK reaction, demonstrated inferior efficiency as compared to... 

The reaction is stereospecific for at least some aliphatic ketones but not for aromatic carbonyl compounds.130 This result suggests that the reactive excited state is a singlet for aliphatics and a triplet for aromatics. With aromatic aldehydes and ketones, the regio-selecitivity of addition can usually be predicted on the basis of formation of the more stable of the two possible diradical intermediates by bond formation between oxygen and the alkene. 

The ene reaction is strongly catalyzed by Lewis acids such as aluminum chloride and diethylaluminum chloride204 Coordination by the aluminum at the carbonyl group increases the electrophihcity of the conjugated system and allows reaction to occur below room temperature, as illustrated in Entry 6. Intramolecular ene reactions can be carried out under either thermal (Entry 3) or catalyzed (Entry 7) conditions 205 Formaldehyde in acidic solution can form allylic alcohols, as in entry 1. Other carbonyl ene reactions are carried out with Lewis acid catalysts. Aromatic aldehydes and acrolein undergo the ene reaction with activated alkenes such as enol ethers in the presence of Yb(fod)3 206 Sc(03SCF3)3 has also been used to catalyze ene reactions.207... 

This work has been extended from aryl and alkyl substituted systems (42) (R = aryl, alkyl) to analogues where R is an amino group, so giving access to synthetic equivalents of the nonstabilized amino nitrile ylides (45). Adducts were obtained in good-to-moderate yield with A-methyhnaleimide (NMMA), DMAD, electron-deficient alkenes and aromatic aldehydes (27,28), and with sulfonylimines and diethyl azodicarboxylate (29). Similarly the A-[(trimethylsilyl)methyl]-thiocarbamates (46) undergo selective S-methylation with methyl triflate and subsequent fluorodesilylation in a one-pot process at room temperature to generate the azomethine ylides 47. 

Autoxidation reaction of alkenes 6-54 Condensation of aromatic aldehydes... 

Many carboxylic acids lose carbon dioxide on either direct or sensitized irradiation, and in some cases (4.10 the evidence points to the operation of an initial electron-transfer mechanism rather than primary a-deavage. Cleavage occurs readily with acyl halides, and this can [ead to overall decarbonylation (4.11). Aldehydes also cleave readily, since the (0=)C—H bond is more prone to homolysis than the (0= C-C bond. This offers a convenient method for replacing the aldehydic hydrogen by deuterium in aromatic aldehydes (4.12. and a similar initial reaction step accounts for the production of chain-Iengtheped amides when formamide is irradiated in the presence of a terminal alkene (4.13). 

Rhodium(II) acetate catalyzes C—H insertion, olefin addition, heteroatom-H insertion, and ylide formation of a-diazocarbonyls via a rhodium carbenoid species (144—147). Intramolecular cyclopentane formation via C—H insertion occurs with retention of stereochemistry (143). Chiral rhodium (TT) carboxamides catalyze enantioselective cyclopropanation and intramolecular C—N insertions of CC-diazoketones (148). Other reactions catalyzed by rhodium complexes include double-bond migration (140), hydrogenation of aromatic aldehydes and ketones to hydrocarbons (150), homologation of esters (151), carbonylation of formaldehyde (152) and amines (140), reductive carbonylation of dimethyl ether or methyl acetate to 1,1-diacetoxy ethane (153), decarbonylation of aldehydes (140), water gas shift reaction (69,154), C—C skeletal rearrangements (132,140), oxidation of olefins to ketones (155) and aldehydes (156), and oxidation of substituted anthracenes to anthraquinones (157). Rhodium-catalyzed hydrosilation of olefins, alkynes, carbonyls, alcohols, and imines is facile and may also be accomplished enantioselectively (140). Rhodium complexes are moderately active alkene and alkyne polymerization catalysts (140). In some cases polymer-supported versions of homogeneous rhodium catalysts have improved activity, compared to their homogenous counterparts. This is the case for the conversion of alkenes direcdy to alcohols under oxo conditions by rhodium—amine polymer catalysts... 

The synthesis of oxetanes by the photochemical 1,2-cycloaddition of the carbonyl function in aldehydes and ketones to alkenes [Eq. (69)] was first reported by Paterno274 in 1909, and later reinvestigated by Biichi 275 in 1954. This reaction has recently been extensively reviewed.276, 277 The formation of the oxetane is apparently the result of addition of excited n, n triplet carbonyl to an alkene, although for certain aromatic aldehydes and ketones the mechanism is less clear.278... 

On the pages which follow, general methods are illustrated for the synthesis of a wide variety of classes of organic compounds including acyl isocyanates (from amides and oxalyl chloride p. 16), epoxides (from reductive coupling of aromatic aldehydes by hexamethylphosphorous triamide p. 31), a-fluoro acids (from 1-alkenes p. 37), 0-lactams (from olefins and chlorosulfonyl isocyanate p. 51), 1 y3,5-triketones (from dianions of 1,3-diketones and esters p. 57), sulfinate esters (from disulfides, alcohols, and lead tetraacetate p. 62), carboxylic acids (from carbonylation of alcohols or olefins via carbonium-ion intermediates p. 72), sulfoxides (from sulfides and sodium periodate p. 78), carbazoles... 

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