Absolute configuration determinations of chiral .alpha.-substituted benzylamines using liquid crystal-induced circular dichroism

Helical Sense and Twisting Power in Thermotropic Side–Chain Copolymers

“…isotropic to nematic transition upon cooling) that might give rise to high HTP values. It is found that in Copolymers (5), (6), and (7), the proximity of T Ch_.l to T precludes adequate supramolecular arrangement in spite of long periods of thermal annealing as seen by the inability to obtain a strong selective reflection peak for AR measurements where TCh._+l and Tg are the cholesteric to isotropic and glass transition temperatures, respectively. However, adding small amounts of p-methoxybenzylidene-p'-butylaniline to the copolymers did reveal a cholesteric texture when observed with hot-stage polarized optical microscopy as demonstrated by Finkelmann and Rehage [22] for a polysiloxane series.…”

“…The helical sense, as defined by the sense of the reflected circularly polarized light [2], and helical twisting power (HTP) characterizing the cholesteric mesophase, are not only intriguing from a fundamental standpoint but also critical to these practical applications. Molecular models based on both steric (short-range) as well as hydrogen bonding (long-range) interactions have been used with reasonable success in interpreting helical sense in low molar mass chiral/nematic mixtures [3][4][5][6][7]. Moreover, the theoretical treatment by Goossens [8] has been successfully used to address several chiral/nematic system parameters including the HTP [9].…”

Novel freebase and zinc bilinone dimers with optically active peripheral groups. Synthesis and application to chiral nematic induction in a nematic mesophase

“…The helical senses of the N * LC samples were determined from the CD spectra of MBBA doped with the FbBL and ZnBL dopants as shown in Fig. 5, indicating that the left-handed (M) N * phases were obtained for the doped MBBA samples [38][39][40]. Thus, the signs of b M were negative for all the FbBL and ZnBL dopants.…”

An Efficient Microwave Method for the Synthesis of Imines

“…In the process, the focus has shifted to a set of imines, (S)-N-(methoxybenzylidene)-a-methylbenzylamines, due to their similarities with (S)-N-(methylbenzyl)benzylamine which has been studied in detail within our group. [8] Classical methods for the synthesis of (S)-N-a-methylbenzylamine derived imines include reaction with an aldehyde by stirring the reaction in dichloromethane (DCM) and 4 Å molecular sieves for 48 h, [9] heating in DCM for 30 min in the presence of K 2 CO 3 , [10] or the use of magnesium perchlorate as a catalyst. [11] Although these methods are successful, reaction times, workup procedures, and the use of expensive or dangerous materials make them less desirable.…”

“…It is clear that this new method A has various synthetic advantages and improvements compared with other pre-existing methods. For example: the use of microwave irradiation significantly reduces reaction times from days to minutes (methods A and B); no perchlorates, which alone are hazardous due to their explosive nature when heating is involved, [11] need to be used (method A versus D and E); and no workup or purification steps are required unlike methods B-E, where extraction, recrystallisation, [9] or distillation [10] is necessary.…”