Reaction with aromatic aldehyde and

Thiazolotriazines 636 (R = CO,Me) were prepared [84JCS(P1)2707] by cycloaddition of dimethyl acetylenedicarboxylate with triazine derivative 632. Derivatives of thiazolo[3,2-b][l,2,4]triazin-3,7-diones 637 have been formed (74JPR163) on reaction with aromatic aldehydes and diazonium salts to give 636 (R = Ar) and 638, respectively. Regioselective catalyzed... 

The Knoevenagel reaction between o-hydroxyaryl aldehydes and ketones and substituted acetonitriles affords high yields of 3-substituted coumarins in aqueous alkaline media <96H(43)1257>, whilst 4-hydroxycoumarins have been elaborated to pyrano [3,2-c]benzopyran-5-ones by reaction with aromatic aldehydes and malononitiile <96P148>. The imine (10) resulting from the complex reaction of o-hydroxyacetophenone with malononitrile undergoes a 1,5-tautomeric shift in solution <96JCS(P1)1067>. 

AYTrimethylsilylmethyl )isothioureas are readily available. They are easily converted into azomethine ylids (synthetic equivalents of iminoazomethine ylids) which, under reaction with aromatic aldehydes and ketones, undergo facile 1,3-cyloaddition to form iminooxazolidine derivatives.472... 

Not only does acetone undergo a highly enantioselective aldol reaction, but hydroxy acetone exhibits excellent stereoselectivity to produce the anti-aldol products 75 (Scheme 2.3d). For example, L-proline catalyzed the aldol reaction between hydroxy acetone and cyclohexanecarbaldehyde to furnish the anti -diol in 60% yield with a greater than 20 1 diastereomeric ratio. The enantiofacial selectivity of the anti-isomer was higher than >99%. Diastereoselectivities are very high with a-substituted aldehydes, whereas low selectivities are recorded in reactions with aromatic aldehydes and with a-unsubstituted aliphatic aldehydes. It is noteworthy that the levels of enantiofacial selectivity for the anti -aldol products... 

The generation of carbanions and their reactions with aromatic aldehydes and ketones... 

More recent patents give an account of o-DAP reactions with aromatic aldehydes and sulphur affording 2-aryl-IPs. A reference to the initial patent containing the description of the above procedure for IP preparation (77SUP566842) was given in (83BRP2113675). Unfortunately this information is absent in (83GEP3132754). 

N. G. Kozlov, S. L. Bondarev, A. P. Kadutskii, L. I. Basalaeva, F. S. Pashkovskii, Russ. J. Org. Chem. 2008, 44, 1031-1037. Tetronic acid in reaction with aromatic aldehydes and 2-naph-thylamine. Investigation of fluorescent and nonlinear-optical characteristics of compounds obtained. 

Glycerol was found to be a very efficient solvent for another catalyst-free three-component reaction furnishing fused pyrans 105, 106, and 161-164 (Scheme 97) [141]. The 2-aminopyran ring was annulated to a variety of scaffolds including 1,3-cyclohexanones, a- and 3-naphthols, 4-hydroxy-6-methyl-2-pyrone, and barbituric acid using the reaction with aromatic aldehydes and methylene active nitriles. It was reported that glycerol recovered from the model reaction (105, Ar = Ph, R = CN, = Me) was reused 20 times in this reaction without... 

Once we have diseussed the results obtained in the reactions with aromatic aldehydes and allylstannanes, we will focus our attention to the results obtained in the Diels-Alder reaetion. 

Table 5 summarizes the reactions of isoprene with aromatic aldehydes and unsaturated aldehydes. Salicylaldehyde provides the expected product as a cyclic boric ester derivative and shows apparently lower stereoselectivity, giving a mixture of 1,3-anti and 1,3-syn isomers in a ratio of 6 1 (run 1, Table 5). 2-Furfural reacts as usual and provides a 1,3-anti isomer as a single diastereomer in good yield (run 2). Unsaturated aldehydes, irrespective of their substitution patterns, undergo homoallylation selectively with excellent 1,3-anti selectivity, the geometry of the double bond of the starting aldehydes remaining intact (runs 3-5). 1,2-Addition to unsaturated aldehyde takes place selectively and no 1,4-addition is observed.

Dendritic molecules with a single triethylene amine core surrounded by hyperbranched polyether sectors catalyze the nitro-aldol reaction between aromatic aldehydes and nitroalkanes (Eq. 3.5).15 The activity of the catalysts decreases when the generation number increases. No significant changes in stereo-control are observed on passing from lower- to higher-generation dendrimers. 

A frequently reported spectrophotometric technique for the determination of hydralazine is based on reactions with aromatic aldehydes to form hydrazones with absorption in the visible region. Luk yanchikova et al (5 +) used p-nitrobenzaldehyde Wesley-Hadzija and Abaffy (55) and Ruggieri (56) used p-dimethylaminobenzaldehyde Luk yanchi-kova (57,58) used cinnamaldehyde Schulert (33) used p-hydroxybenzaldehyde and Zak et al (59) used p-methoxy-benzaldehyde, after testing cinnamaldehyde, salicylaldehyde, 3, +,5-trimethoxybenzaldehyde, and 1-naphthaldehyde. 

Although the sulfur trifluoride compounds are generally useful as selective agents for conversion of carbonyl and carboxyl groups to difluoromethylene and trifluoromethyl groups, variations in reaction conditions are often necessary.7 Thus the reaction of aromatic ketones requires heating at 150°. Since the reaction with aliphatic aldehydes and ketones is exothermic, it is advan-... 

For example, Nakamura and Kuwajima [15] have described 1-alkoxy-l-trimethylsilyloxycyclopropanes (15) -prepared by reductive silylation of alkoxy 3-chloropropanoates-, which react with aliphatic aldehydes, but not with ketones, in the presence of one equivalent of TiCl4 to give good yields of y-lactones 17 through the acyclic derivative ethyl 4-hydroxybutanoate (16) (Scheme 5.10). With aromatic aldehydes and their acetals the reaction leads directly to acyclic 1,4-D derivatives. 

Physical organic experiments have shown that simple organolithinm reagents exist as aggregates in solution and react with aromatic aldehydes and ketones as a monomer. In most cases, the reactions are initiated by ET, as in Grignard reactions, althongh... 

A vast array of piperidine containing cores, both natural and synthetic, are of biological and medicinal interest. These heterocyclic scaffolds have been the subjects of considerable synthetic efforts, especially for the construction of optically active compounds. In this context, Khan et al. reported a catalytic bromodi-methylsulfonium bromide (BDMS) three-component reaction of 1,3-dicarbonyls with aromatic aldehydes and aromatic amines for a facile access to highly functionalized piperidines (Scheme 24) [104]. This strategy is an interesting illustration of... 

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. 

A -Cyano- and A -(p-toluenesulfonyl)-A -(trimethylsilylmethyl)-5-methylisothio-ureas 269a and 269b have also been utilized as synthetic equivalents of azomethine ylides. ° Reaction of 269a and 269b with aromatic aldehydes and aryl ketones, in the presence of CsF, gives 2-iminooxazolines 270a-e in modest-to-good yield. These 2-iminooxazolines apparently are stable to isolation and do not isomerize to 2-aminooxazolines (Scheme 8.76). 

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