Thio aldehydes

Thio aldehydes (178) in situ smoothly react with silyl ether of nitroethane, and regioselectively form cycloadducts (179) as one isomer or as a mixture of stereoisomers in high yields. 

In such experiments, a preliminary preparation of the often difficulty obtainable pure thioaldehydes is not actually necessary. It suffices to bring the fermenting yeast in contact with the ordinary (non-thio) aldehydes and with ammonia and hydrogen sulfide (ammonium hydrogen sulfide). Such conditions frequently apply for animals and plants, for example, in bacteriological processes and probably also in the metabolism of higher organisms. 

The second step in the hexose synthesis was the aldol condensation of 4 with another a-hetero aldehyde derivative S. By tuning the Lewis acid and the solvent, three of the four possible diastereomeric products could be selectively prepared. a-Amino and a-thio aldehydes worked well also, leading to 9 and 10 respectively. 

Rule 3 correctly predicts the experimentally observed thiophilic addition. Simple thio-aldehydes and thioketones always have a greater LUMO coefficient at C than S. The results are opposite here and this reversal reflects the experimental results nicely. 

Early attempts to prepare selenoaldehydes by treatment of aldehydes with H2Se under acidic conditions yielded oligomeric or polymeric sele-nides, possibly via self-condensation of selenoaldehydes [15JPR116 67JCS(B)117]. In 1988, Japanese workers reported that the reaction of aldehydes with bis(trimethylsilyl)selenide in the presence of a catalytic quantity of butyl lithium afforded selenoaldehydes (88JA1976). This novel method has been exploited for the first intramolecular Diels-Alder reactions of selenoaldehydes (88TL6965). Dienal (79) was converted into dienselenal (80) and then into a mixture of stereoisomeric adducts 81 and 82. The major product was as-fused isomer 81, derived from the endo transition state. These results compare favorably with intramolecular thio-aldehyde reactions (Section II,B). 

Te-O bonds, 453 Te-P bonds, 454 Te-S bonds, 453 Te-Sb bonds, 456 Te-Se bonds, 453 Te-Te bonds, 454 Tellurium cations, 938-942 anions, 1349 cations, 1346-1349 Th-contaming species neutrals, 643-650 Th clusters, 650-651 Thiazyl compounds NSR N-S bonds, 420 -421 Thio-acid RC(0)SH S-C bonds, 438 S-H bonds, 438 Thio-aldehydes RC(S)H C-H bonds, 125 Thio-amides RC(S)NR2 ... 

Phenacyl sulfides are known to undergo three main processes from their triplet state 1.) charge transfer from the heteroatom to the carbonyl group [27-29], 2.) cleavage of the bond between the C-atom next to the carbonyl C-atom and the S-atom (so-called P-cleavage) [28,29], and 3.) y-hydrogen abstraction by the carbonyl 0-atom with subsequent cleavage of the same C-S bond as above in the 1,4-biradical [30,31]. This last sequence is used to obtain thio-aldehydes which can be trapped by enes or dienes (Scheme 5). 

The thione (201), derived from the Diels-Alder reaction of transient thio-aldehydes, is a novel precursor to seven-membered rings, and, as part of the... 

Halogeno-, nitro- and thio- aldehydes with ammonia... 

Nucleophilic additions to a,3-dialkoxy aldehydes via allyl silanes (eq 3) or silyl ketene acetals (Mukaiyama reaction) (eq 4) exhibit similarly high selectivities. a-Thio aldehydes also react under MgBr2-catalyzed Mukaiyama conditions with efficient stereocontrol (eq 5). ... 

The Pd-catalyzed hydrogenoiysis of acyl chlorides with hydrogen to give aldehydes is called the Rosenmund reduction. Rosenmund reduction catalyzed by supported Pd is explained by the formation of an acylpalladium complex and its hydrogenolysis[744]. Aldehydes can be obtained using other hydrides. For example, the Pd-catalyzed reaction of acyl halides with tin hydride gives aldehydes[745]. This is the tin Form of Rosenmund reduction. Aldehydes are i ormed by the reaction of the thio esters 873 with hydrosilanes[746,747]. 

Diaryl disulfides and diselenides add to alkynes to afford the (Z)-l, 2-bis(ar-ylthio)alkenes 193 and (Z)-l,2-bis(arylseleno)alkenes 194. Under CO pressure, carbonylative addition takes place to give thio esters and the selenoketones 195[I07], The selenoketones are converted into the /J-seleno-a, 3-unsaturated aldehydes 196 by Pd-catalyzed hydrogenolysis with HSnBu3[108,109],... 

Halogenated- ,/S-unsaturated ketones or aldehydes are reacted with methyl thioglycolate and cyclized with alkali alcoholate/ Thus jS-bromobenzalacetone (75) gives methyl 3-methyl-5-phenyl-2-thio-phenecarboxylate (76) and from a-methyl-j5-chlorocrotonaldehyde (77), 4,5-dimethyl-2-thiophenecarboxylate (78) is obtained. 

Aldehydes have also been obtained by lithium trialkoxyaluminum hydride reduction of 5-nitriles or 5-acid chlorides, and, as the thio-semicarbazones, by the McFadyen-Stevens reaction in surprisingly good yields (50-60%) considering the severity of the reaction conditions. ... 

Substituted TMM complexes also cycloadd to aldehydes in the presence of a tin cocatalyst such as MesSnOAc and MesSnOTs [31]. Reaction of 2-heptenal with methyl precursor (6) gave a mixture of methylenetetrahydrofurans (68) and (69). This regioselectivity is reversed with 10-undecenal and methyl precursor (5), where adduct (70) now predominates over (71). As in the carbocyclic system, the phenylthio group also functions as a regiocontrol element in reaction with cyclohexyl aldehyde. The initially formed adduct (72) eliminates the element of thio-phenol on attempted allyl rearrangement, and the overall process becomes a cycloaddition approach to furans (Scheme 2.21) [20]. 

The Michael reaction occurs with a variety of a,/3-unsaturated carbonyl compounds, not just conjugated ketones. Unsaturated aldehydes, esters, thio-esters, nitriles, amides, and nitro compounds can all act as the electrophilic acceptor component in Michael reactions (Table 23.1). Similarly, a variety of different donors can be used, including /3-diketones, /3-keto esters, malonic esters, /3-keto nitriles, and nitro compounds. 

Simple 1-hetero-substituted allyllithium derivatives, such as 1-alkoxy-94"96, 1-alkyl-thio-50,97, 1-phenylselenyl-54,98 show insufficient regio- and simple diastereoselectivity in their reaction with aldehydes. The rcgiosclectivity is greatly enhanced in favor of the a-products by in... 

A somewhat tedious extension of this methodology, which guarantees good induced stereoselectivity, relies on the reversible introduction of an a-substituent which is removed after the aldol addition is performed. For this purpose, the corresponding derivative of (methyl-thio)acetic acid is converted into the boron enolate and subsequently reacted with aldehydes. The... 

The proline derived diamines 2 and 4 (vide supra) are also suitable chiral additives in enantiose-lective additions of a-unsubstituted enolates. Best results are obtained with the naphthyl derivative, as demonstrated in the tin(II) triflate mediated addition of the O-silylketene thio-acetal l-toT-butylthio-l-trimethylsilyloxyethane to aldehydes which delivers 3-hydroxythio esters in optical purities of up to 95% ee and chemical yields between 50 and 90 %24... 

Natrium-tri thio-dihydrido-borat reduziert Aldehyde und Ketone in THF bei 20° in guten Ausbeuten zu Alkoholen, wahrend bei Siedetemperatur aus Aldehyden undof-fenkettigen Ketonen auch Disulfane, aus cyclischen Ketonen auch Tetrasulfane gebil-det werden3 z.B. ... 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

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