4248-77-5Relevant articles and documents
Reduction of alkyl and vinyl sulfonates using the CuCl2· 2H2O-Li-DTBB(cat.) system
Radivoy, Gabriel,Alonso, Francisco,Moglie, Yanina,Vitale, Cristian,Yus, Miguel
, p. 3859 - 3864 (2007/10/03)
The reduction of a series of alkyl mesylates, dimesylates and triflates to the corresponding hydrocarbons was efficiently performed using a reducing system composed of CuCl2·2H2O, an excess of lithium sand and a catalytic amount (5 mol%) of 4,4′-di-tert-butylbiphenyl (DTBB), in tetrahydrofuran at room temperature. The process was also applied to enol and dienol triflates affording alkenes and dienes, respectively. The use of the deuterated copper salt CuCl2·2D2O allowed the simple preparation of the corresponding deuterated products.
Novel Ion Containing Liquid Crystals and Liquid Crystalline Main Chain Polymers Based on Trans-1,2-Bis(4-Pyridyl Ethylene) Mesogen
Cheng, P.,Blumstein, A.,Subramanyam, S.
, p. 1 - 38 (2007/10/02)
Ion bearing liquid crystalline compounds based on trans-1,2-bis(4-pyridinium)ethylene were synthesized and studied.These compounds included low molecular mass analogues, twin model compounds and main chain ionomers.Most of these exhibited liquid crystallinity of the smectic type.As a general rule the introduction of charges into the mesogenic moiety increased the stability (transition temperature) of the mesophase.Large supercooling effects, broad mesophase intervals and tendency to polymorphism are common features of these ionic mesogenic compounds.In the case of twin model compounds a variety of smectic phases were observed.The nature of these was dependent on the nature of the counterion and the thermal history of the compound.Tosylate or p.toluene sulfonate counterions promoted a higher degree of order in smectic mesophases as well as higher transition tempertures compared to methylsulfonate counterions.A pronounced odd-even effect of the isotropisation temperature of the twin compounds was observed.Compounds with even numbered methylene spacers display higher transition temperatures than those with an odd spacer.Only polymers with methylsulfonate and toluenesulfonate counterions were found to exhibit both, thermotropic and lyotropic mesophases.Thermotropic mesophases were characterized as smectic mesophases of lower order (SA).The nature of lyotropic mesophases were not determined.High transition temperatures and concommitant oxydative crosslinking made the study of polymers with halogen counterions difficult.Polymers with halogen and perchlorate counterions were found fo be poorly soluble in water precluding the formation of lyotropic mesophases.The introduction of a few siloxane bonds into the flexible spacer joining the charged mesogen moieties has a dramatic effect on lowering the transition temparatures and making possible the study of mesophases up to their isotropisation temperature.Preliminary characterization of polymers with siloxane containing spacer and methylsulfonate/tosylate counterions suggest a smectic mesophase of lower order. - Keywords: Ion containing liquid crystals, liquid crystal ionomers
