23838-12-2Relevant academic research and scientific papers
Desorption Chemical Ionization Mass Spectrometry of Epimeric 3-Hydroxysteroids and Derivatives. Stereoselectivity and Nucleophilic Substitution with Ammonia
Tecon, Pierre,Hirano, Yutaka,Djerassi, Carl
, p. 277 - 285 (1982)
The desorption chemical ionization mass spectra, using ammonia as reagent gas, of several epimeric 3-hydroxysteroids and their ether and carboxylic acid ester derivatives are reported.In the case of steroids possessing a Δ4- or Δ5-3α-benzoate moiety, stereospecific stabilization of the protonated molecular ion + is observed.This behaviour is rationalized in terms of interaction of the double bond and the protonated benzoate group at C-3.Nucleophilic substitution by NH3 is observed when a double bond is present in the vicinity of the substitution center.The nature and the stereochemistry of the leaving group influence this substitution reaction.Our results seem to indicate the operation of a two-step mechanism (e.g.SN1 type reaction) rather than a SN2 type mechanism for the formation of the substitution ion +.
Br?nsted Acid Mediated Nucleophilic Functionalization of Amides through Stable Amide C?N Bond Cleavage; One-Step Synthesis of 2-Substituted Benzothiazoles
Biswas, Srijit,Biswas, Subrata,Duari, Surajit,Elsharif, Asma M.,Maity, Srabani,Roy, Arnab
supporting information, p. 3569 - 3572 (2021/07/22)
We have developed a Br?nsted acid mediated synthetic method to directly cleave stable amide C?N bonds by a variety of alcohol and amine nucleophiles. Reverse reactivity was observed and alcoholysis of amides by activated primary and secondary benzylic, and propargylic alcohols have been achieved instead of the expected nucleophilic substitution of alcohols. As an application, 2-substituted benzothiazole derivatives have been synthesized in one pot employing 2-aminothiophenol as nucleophile.
Cross-linked liquid crystalline polybenzoxazines bearing cholesterol-based mesogen side groups
Liu, Ying,Chen, Jiming,Qi, Yongxin,Gao, Sheng,Balaji, Krishnasamy,Zhang, Yaoheng,Xue, Qingbin,Lu, Zaijun
, p. 252 - 260 (2018/05/23)
A cross-linked liquid crystalline polybenzoxazine [poly(BA-ac)] was synthesized for the first time from a novel bifunctional benzoxazine monomer (BA-ac) containing cholesterol-based mesogens. The monomer was synthesized using cholesteryl 4-aminobenzoate, bisphenol-A, and paraformaldehyde as raw materials via Mannich reaction. Subsequently, the cross-linked polybenzoxazine bearing cholesterol-based mesogen side groups was obtained through thermally induced ring-opening polymerization of the benzoxazine ring. The study results show that BA-ac is a monotropic smectic C liquid crystal, and poly(BA-ac) contains a smectic C phase structure. The formation of the liquid crystalline structure of poly(BA-ac) is mainly caused by the strong ability of cholesterol-based mesogen to form liquid crystals and its position on the side group of the cross-linked network. Due to the existence of a liquid crystal structure, poly(BA-ac) has high thermal conductivity. Its coefficient of thermal diffusivity is 31% higher than that of a traditional polybenzoxazine poly(BA-a). Poly(BA-ac) also has high heat-resistance. Its glass transition temperature, 5% and 10% weight loss temperatures are 175 °C, 306 °C, and 321 °C, respectively.
A liquid-crystalline poly(iminomethylene) with cholesterol-containing pendant groups
Walree, C. A. van,Pol, J. F. van der,Zwikker, J. W.
, p. 561 - 565 (2007/10/02)
Two poly(iminomethylenes) with cholesterol-containing pendant groups were synthesized.Using an aliphatic spacer, a liquid-crystalline polymer was obtained, with equal amounts of right- and left-handed helices.With phenylene as bridging group, only oligomers resulted, probably for steric reasons.Some novel liquid-crystalline esters of cholesterol are also presented.
