Lead compounds condensation products

Lithio ethyl acetate is prepared in quantitative yield by reaction of LHMDS with ethyl acetate in THF at —78 °C. Reaction with carbonyl compounds leads to condensation products in high yield (eqs 3 and 4). No racemization of the a-silyloxy esters occurs (eq 4). 

This chapter contains a review of some photodimerizations and photo-condensations leading to the formation of substituted cyclobutanes. Since the literature in this field is indeed vast, it would be impossible to present here a comprehensive review of all the reactions reported to lead to such products. Instead, it is our goal to present a general survey of the various types of compounds known to produce cyclobutane compounds upon irradiation and to discuss mechanisms which have been proposed to account for some of these products. 

The reaction sequence starts from tetrazolyldiazonium salt 42 prepared from aminotetrazole 41 by diazotation. This compound when reacted with arylformylacetonitrile 43 leads to the intermediate formation of the condensation product 44, which easily undergoes ring closure to 45. This tetrazolo[5,l-z][l,2,4]triazine compound, however, forms an equilibrium with the valence bond isomeric azide 46, which can participate in a different ring closure than the reverse route, and yields the tetrazolo[l,5-A][l,2,4]triazine product 47. The reaction was carried out with a series of various aryl derivatives and proceeded in good to excellent yields (68-87%). 

Several cross-aldol condensations have been performed with alkaline earth metal oxides, including MgO, as a base catalyst. A general limitation of the cross-aldol condensation reactions is the formation of byproducts via the self-condensation of the carbonyl compounds, resulting in low selectivities for the cross-aldol condensation product. For example, the cross-condensation of heptanal with benzalde-hyde, which leads to jasminaldehyde (a-K-amylcinnamaldehyde), with a violet scent... 

LXVIII), a constituent of aviation fuel. The reaction of acetone with acetylene may also lead to developments of importance in finding new uses for acetone. For example, acetone reacts with acetylene in the presence of a metal acetylide catal5rst to form the compound LXIX, which could be converted into isopentane (LXX), another constituent of aviation fuel. There may be possibilities of using the condensation products of acetone such as mesityl oxide (LXXI), which could be converted through the saturated ketone, methyl isobutyl ketone (LXXII), into 4-methylpentane (LXXIII). 

Furfural A colorless liquid which changes to reddish brown upon exposure to light and air. Furfural forms condensation products with many types of compounds including phenols and amines. If present in kerosene or jet fuel, furfural may lead to color degradation. 

The addition of a phenylsulfoxide moiety to the end of the side chain markedly changes the activity of this class of compounds. This product, sulfinpyrazone (97-11), stimulates uric acid excretion, making it a valuable dmg for dealing with the elevated serum uric acid levels associated with gout. The compound is stiU one of the more important uricosuric agents available today. The starting ester (96-9) is available by alkylation of the dianion from ethyl malonate with 2-chloroethylphenyl thioether. Condensation with diphenylhydrazine (97-3) in the presence of a base then affords the pyrrazolodione (97-10). Oxidation of sulfur with a controlled amount of hydrogen peroxide leads to the sulfoxide and thus sulfinpyrazone (97-11) [107]. 

The starting material (48-1) for a pyrrazolopyridazine can be obtained by treating the corresponding enol, which is simply the condensation product of methylmaleic anhydride and hydrazine, with phosphorus oxychloride. Reaction with piperazine leads to the displacement of the sterically more accessible chlorine to afford the alkylation product (48-2). Treatment with hydrazine leads to the replacement of the remaining halogen and the formation of (48-3). The missing carbon is, in this case, supplied by formamide to afford zindotrine (48-4) [51], a compound that shows activity as a bronchodilator. 

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