Homologation-condensation

Tetrahydrophthalides. The I esters is rendered regioselective bs the combination of the alkoxymagne Homologation-condensation. vinylmagnesium halide also triggen Bridged ring compounds can be prej... 

Homologation-condensation. The reaction of cyclic p-keto esters with a vinylmagnesium halide also triggers oxy-Cope rearrangement and Claisen condensation. Bridged ring compounds can be prepared by this method. ... 

Homologation-condensation. 3-Acyltetramic acids are accessible from N-acylacetylglycine esters. In turn the latter compounds may be assembled from a-diazo acetamide derivatives and aldehydes with elimination of dinitrogen. Zirconium chloride is a useful catalyst. 

Condensed Benzimidazoles of Type 6-5-5 Condenses Benzimidazoles of Type 6-5-6 Condensed Benzimidazoles of Type 6-5-7 and Higher Homologs Condensed Benzimidazoles Bridged Between N-1 and C-7... 

High diastereofacial selection has been found in condensations between a-methyl-aldehydes (250) and the dithioacetate enolate (251) the syn-isomers (252) predominate in these and homologous condensations using the lithium enolate of ethyl... 

In the sections below a brief overview of static solvent influences is given in A3.6.2, while in A3.6.3 the focus is on the effect of transport phenomena on reaction rates, i.e. diflfiision control and the influence of friction on intramolecular motion. In A3.6.4 some special topics are addressed that involve the superposition of static and transport contributions as well as some aspects of dynamic solvent effects that seem relevant to understanding the solvent influence on reaction rate coefficients observed in homologous solvent series and compressed solution. More comprehensive accounts of dynamics of condensed-phase reactions can be found in chapter A3.8. chapter A3.13. chapter B3.3. chapter C3.1. chapter C3.2 and chapter C3.5. 

In 1880, Liebermann and Voltzkow (40), and then Voltzkow (41), condensing chloroacetic acid with both ethyl N-phenylthiocarbamate and p-tolylisothiocyanate obtained homologous compounds to which they attributed formulas 40 and 41, whereas their structure probably derives from that of 38 by substituting an aryl group on the cyclic nitrogen. 

Hoffmaim-La Roche has produced -carotene since the 1950s and has rehed on core knowledge of vitamin A chemistry for the synthesis of this target. In this approach, a five-carbon homologation of vitamin A aldehyde (19) is accompHshed by successive acetalizations and enol ether condensations to prepare the aldehyde (46). Metal acetyUde coupling with two molecules of aldehyde (46) completes constmction of the C q carbon framework. Selective reduction of the internal triple bond of (47) is followed by dehydration and thermal isomerization to yield -carotene (21) (Fig. 10). 

Darzens glycidic ester condensation generally involves the condensation of an aldehyde or ketone 2 with the enolate of an a-halo ester 1 which leads to an a,P-epoxy ester (a glycidic ester) (3). Thus the reaction adds two carbons to the electrophile however, the reaction has been primarily developed as a one-carbon homologation method. That is, subsequent to the condensation, the ester is saponified and decarboxylation ensues to give the corresponding aldehyde or ketone 5.2... 

Instead of a-halo esters, related reactants can be used e.g. the a-halo derivatives of ketones, nitriles, sulfones and A,A-disubstituted amides. The Darzens condensation is also of some importance as a synthetic method because a glycidic acid can be converted into the next higher homolog of the original aldehyde, or into a branched aldehyde (e.g. 5) if the original carbonyl substrate was a ketone ... 

The ring-contracted analog of alphaprodine is prepared by a variation of the scheme above. Alkylation of 109 with ethyl bromoacetate affords the lower homolog diester (115). Dieckmann cyclization followed by saponification-decarboxylation yields the pyrrolidine (116). Reaction with phenylmagnesium bromide leads to the condensation product (117) acylation with propionic anhydride gives the analgesic agent prolidine (118)... 

Wilkinson s catalyst 117,345,777 Wittig condensation 73 Wittig homologation 503 Wittig methylenation 649 Wittig reaction 17, 68 f., 86 f.,... 

The first C40 carotenoid, phytoene, is produced by head-to-head condensation of two GGPPs by an enzyme that shares homology to GGPPS and squalene synthases... 

Hirano T, Kobayashi R, Hirano M 1997 Condensins, chromosome condensation protein complexes containing XCAP-C, XCAP-E and a Xenopus homolog of the Drosophila Barren protein. Cell 89 511-521... 

A classic method14 for examining the thermochemical regularity of an organic homologous series is plotting the standard molar enthalpies of formation versus the number of carbon atoms in the compounds. The linear relationship may be expressed as equation 1 where all the enthalpies of formation are in either the gaseous or a condensed phase, a is the slope, ft is the y-intercept and nc is the number of carbon atoms in the compound. 

Influence of subphase temperature, pH, and molecular structure of the lipids on their phase behavior can easily be studied by means of this method. The effect of chain length and structure of polymerizable and natural lecithins is illustrated in Figure 5. At 30°C distearoyllecithin is still fully in the condensed state (33), whereas butadiene lecithin (4), which carries the same numEer of C-atoms per alkyl chain, is already completely in the expanded state (34). Although diacetylene lecithin (6) bears 26 C-atoms per chain, it forms both an expanded and a condensed phase at 30°C. The reason for these marked differences is the disturbance of the packing of the hydrophobic side chains by the double and triple bonds of the polymerizable lipids. At 2°C, however, all three lecithins are in the condensed state. Chapman (27) reports about the surface pressure area isotherms of two homologs of (6) containing 23 and 25 C-atoms per chain. These compounds exhibit expanded phases even at subphase temperatures as low as 7°C. 

The preparation of diarylthiophene -was described by Campaigne and coworkers (13). The condensation of thiophene and its homologs with ketones was also investigated (67) ... 

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