Synthesis and Characterisation of Macrocyclic Diamino Chiral Crown Ethers
A benign and efficient synthesis of chiral macrocyclic ‘aza-crown’ ethers of varying ring size is reported. The synthesis involves a Schiff base condensation of ether linked dialdehydes of varying chain length and (1R,2R)-(–)-1,2-diaminocyclohexane under mild conditions to yield the macrocycles, which are subsequently reduced to yield the diamino analogues.
Novel Gemini Micelles from Dimeric Surfactants with Oxyethylene Spacer Chain. Small Angle Neutron Scattering and Fluorescence Studies
Three new gemini surfactants containing mono-, di-, and trioxyethylene spacer chains have been synthesized. Small angle neutron scattering (SANS) cross sections from the micellar aggregates of these dimeric amphiphiles Br-, n-C16H33NMe2+-CH2(CH2OCH2)(p)CH2-N+Me2-n-C16H33,Br-, (where p = 1, 2, and 3) in aqueous media (D2O) have been measured. The data have been analyzed using the Hayter and Penfold model for macro-ion solution to compute the interparticle structure factor S(Q) taking into account the screened Coulomb interactions between the dimeric micelles. The SANS analysis showed that the micellar morphology depends on both the nature and the length of the spacer unit. Detailed analysis of the data further indicates that the introduction of oxyethylene spacer is not sufficient enough to prevent looping of the spacer chain. Thus the average separation between the dimethylammonium ion headgroups is considerably lower than is expected from a fully extended conformation of the spacer chain. The micelles from these surfactants have also been characterized in terms of their critical micelle concentrations (cmc), microviscosities, and micropolarities on the basis of the information provided by micelle-solubilized fluorescent probes. These results indicate little difference in their micellar properties such as cmc, microviscosity, and micropolarity.
3,1‐Benzoxazine und Tetrahydrochinazoline aus o‐Aminobenzylalkohol und o‐Aminobenzylamin ‐ Semi‐empirische MO‐Berechnungen zum Cyclisierungsverhalten
o‐Aminobenzylalkohol (4) kondensiert mit Aldehyden und Ketonen zu den 3,1‐Benzoxazinen 20a/b und 22a/b, mit β‐Diketonen hingegen entstehen die Enaminderivate 24a‐c. Mit dem isosteren o‐Aminobenzylamin (1) ergeben sich als heterocyclische Produkte die Tetrahydrochinazoline 11a/b und 14b, 1,4‐Diamine wie 2 und 3 reagieren zu den offenkettigen Verbindungen 15, 16b, 18a und 19. Das unterschiedliche Verhalten kann mit den Reaktionsenthalpien, die mit dem semi‐empirischen MNDO‐Verfahren berechnet wurden, erklärt werden.