Search results for "condensation"

Stereoselective Synthesis of Bromopiperidinones and their Conversion to Annulated Heterocycles

2009

N-Galactopyranosyl- and N-glucopyranosyl imines of aliphatic, aromatic and heteroaromatic aldehydes react with 1-methoxy-3-trimethylsilyloxy-1,3-butadiene in a domino Mannich-Michael reaction cascade to give 2-substituted 5,6-dehydro-piperidin-4-ones with high diastereoselectivity. Treatment of these cyclic enaminones with N-bromo-succinimide yields the corresponding 2-substituted 5-bromo-5,6-dehydropiperidinones which react with L-SelectrideⓇ or methylcuprate to afford the saturated bromo-piperidinones with high diastereoselectivity. Condensation reactions of these products with thioamides afford thiazolopiperidines

Polypropylenglykol in lösung, zahlenmittelmolekulargewicht und reibungsverhalten

1967

Es wird uber Molekulargewichtsbestimmungen an Polypropylenglykol mittels Messungen der Erhohung der Kondensations- und der Siedetemperatur berichtet. Hierzu wird ein neues Gerat zur Bestimmung der Kopdensationstemperaturerhohung benutzt, das mit 8 Thermoelementen arbeitet. Die physikalisch ermittelten Mn-Werte sind etwas niedriger als die sich aus der Hydroxylzahl ergebenden chemisch erumittelten Mn-Werte. Das Losungsverhalten wird durch Diffusionsmessungen untersucht, die in Aceton und Benzol ausgefuhrt wurden. Es ergeben sich von Mn = 4000 bis hinab zu sehr niedrigen Molekulargewichten Diffusionskoeffizienten, die durch konstante Exponenten b in D = K·M−b dargestellt werden konnen. In Ace…

ChemInform Abstract: Synthesis, Luminescence, and Condensation of Oligo(phenylenevinylene)s with Alkoxysilane End Groups

2009

Exploring the potential of some yeast strains in the stereoselective synthesis of aldol reaction products and its reduced 1,3-dialcohol derivatives

2013

Abstract The behavior of two yeast strains has been studied under different conditions. Both microorganims catalyzed the aldol reaction between activated aldehydes and acetone when a large amount of the latter was present in the reaction medium producing, with moderate stereoselectivity, the aldol product with the R configuration. No reduction of any of the products present in the medium was detected. On the other hand, the carbonyl group of the racemic aldol was reduced to produce chiral 1,3-dialcohol derivatives when water was employed as the only solvent. In this case, the resolution of the racemic starting material was also possible with one of the biocatalysts, and the aldol was recove…

Antimykotische Wirkstoffe, 18. Mitt. Aromatisch substituierte 2-(4-Toluidino)pyrimidine

1985

Die Kondensation von 4-Tolylguanidin (1) mit den aromatische und heteroaromatische Substituenten tragenden β-Diketonen 2a–d fuhrt zu den korrespondierend substituierten 2-(4-Toluidino)pyrimidinen 3a–d. Antimycotic Agents, XVIII: Aromatically Substituted 2-(4-Toluidino)pyrimidines Condensation of 4-tolylguanidine (1) with the β-diketones 2a–d bearing aromatic or heteroaromatic substituents leads to the 2-(4-toluidino)pyrimidines 3a–d.

Synthesis, crystal structure and magnetic properties of a new [ZnII6DyIII6] dodecanuclear motif

2013

Abstract A new dodecanuclear complex, [{(HL)(L)(dmf)ZnIIDyIII(dmf)(H2O)}6]·3dmf·4.2H2O has been assembled using a supramolecular compartmental ligand (H3L results from the condensation reaction of 3-formylsalicylic acid and hydroxylamine). The six DyIII ions describe an octahedron that is inscribed into the octahedron generated by the zinc(II) ions each DyIII ion from this motif behaving as a single ion magnet.

Synthesis and Tautomerization of 6,7-Dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines.

2007

The condensation of 5-amino-4-phenyl-1,2,3-triazole (1) with chalcones 2a-e or 3-dimethylamino-propiophenone (4f) leads to the 6,7-dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines 3a-f. The equilibrium of 3 and the tautomeric 4,7-dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines 3′ is described.

Selective derivatisations of resorcarenes - 2. Multiple regioselective ring closure reactions

1997

Abstract The condensation of the C-pentyl resorcarene 1 with long chain aliphatic diamines 3a-d and excess formaldehyde leads under high dilution conditions to tetrabenzoxazine derivatives 4a-d in which pairs of adjacent oxazine rings are connected by an aliphatic chain. Six new rings are formed per resorcarene molecule during this reaction in a regioselective way. For one example (4a) the chiral cleft-like structure with C2 symmetry was proved by single crystal X-ray analysis. Hydrolysis of the oxazine rings gives the secondary amine derivatives 5a,b with C2v symmetry in high yield.

ChemInform Abstract: Stereoselective Synthesis of Bromopiperidinones and Their Conversion to Annulated Heterocycles.

2010

N-Galactopyranosyland N-glucopyranosyl imines of aliphatic, aromatic and heteroaromatic aldehydes react with 1-methoxy-3-trimethylsilyloxy-1,3-butadiene in a domino Mannich-Michael reaction cascade to give 2-substituted 5,6-dehydro-piperidin-4-ones with high diastereoselectivity. Treatment of these cyclic enaminones with N-bromo-succinimide yields the corresponding 2-substituted 5-bromo-5,6-dehydropiperidinones which react with L-Selectride R © or methylcuprate to afford the saturated bromo-piperidinones with high diastereoselectivity. Condensation reactions of these products with thioamides afford thiazolopiperidines.

Synthesis of peptides with α,β-dehydroamino acids, VI. Synthesis ofN-benzyloxycarbonyl andN-trifluoroacetyl dipeptides of α,β-dehydro-butyrine, -vali…

1988

Condensation of Z- and TFA-amino acid amides with 2-oxo-acids, namely butanoic, 3-methylbutanoic, 4-methylpentanoic, and (3RS)-3-methylpentanoic acid, yields (in the presence of p-toluenesulfonic acid as a catalyst) Z- and TFA-dipeptides with C-terminal ΔAbu2) (1–4), ΔVal (5–8), ΔLeu (9–11), and ΔIle (12–15) (Table 1).