Synthesis of novel β-aminocyclobutanecarboxylic acid derivatives by a solvent-free aza-Michael addition and subsequent ring closure

Novel beta-aminocyclobutanecarboxylic acid derivatives were prepared via a sequential solvent-free aza-Michael addition of benzophenone imine across 3-halopropylidenemalonates and base-induced ring closure. These highly substituted cyclobutanedicarboxylic acid derivatives were subjected to a reactivity study which demonstrated the tendency of these donor-acceptor substituted four-membered rings to be converted into their corresponding ring-opened products

Managerial cost and budget control in petroleum refining

Thesis (M.B.A.)--Boston UniversityThe elemental object of business is to provide a commodity or service to tbe consumer at a profit.* Business in the United States is perpetuated through competition, and in order for any one company to succeed in the fundamental objective, it must meet such competition successfully

Synthesis and analysis of stable isotope-labelled N-acyl homoserine lactones

Aliphatic aldehydes were deuterated at the alpha-position via a base-catalyzed exchange reaction with D2O. These deuterated building blocks were used for the synthesis of labelled analogues of quorum sensing signal molecules belonging to the three major classes of naturally occurring N-acylated homoserine lactones (AHLs), with the label on a non-enolizable and therefore stable position. Besides the application of these stable isotope-labelled AHLs as a labelled standard for analysis via isotope dilution mass spectrometry, these compounds can be used to study the metabolic fate of the fatty acid tail of the AHL-molecule. These isotope-labelled compounds were fully characterized and used to synthesize the deuterated analogues of two commonly occurring AHL-degradation products, a tetramic acid and a ring opened N-acyl homoserine

Synthesis and biological evaluation of novel N-α-haloacylated homoserine lactones as quorum sensing modulators

Novel N-α-haloacylated homoserine lactones, in which a halogen atom was introduced at the α-position of the carbonyl function of the N-acyl chain, have been studied as quorum sensing (QS) modulators and compared with a library of natural N-acylated homoserine lactones (AHLs). The series of novel analogues consists of α-chloro, α-bromo and α-iodo AHL analogues. Furthermore, the biological QS activity of the synthetic AHL analogues compared to the natural AHLs was evaluated. Halogenated analogues demonstrated a reduced activity in the Escherichia coli JB523 bioassay, with the α-iodo lactones being the less active ones and the α-chloro AHLs the most potent QS agonists. Most of the α-haloacylated analogues did not exhibit a significant reduction when tested in the QS inhibition test. Therefore, these novel analogues could be utilized as chemical probes for QS structure–activity studies

Nematic liquid crystal devices with sub-millisecond response time

Conventional nematic liquid crystal devices exhibit switching times that are in the order of several milliseconds. In this work we focus on two types of nematic liquid crystals that can overcome the limitations of conventional nematic liquid crystals and allow sub-millisecond switching times for both switching on and off: nano-pore polymer-liquid crystals and dual-frequency liquid crystals

Synthesis and reactions of 1-amino-1,5,6,10b-tetrahydroimidazo[2,1-a]isoquinolin-2(3H)-ones

1-Amino-1,5,6,10b-tetrahydroimidazo[2,1-a]isoquinolin-2(3H)-ones, as previously unknown ring-annelated isoquinolines with a 3-aminoimidazolidin-4-one scaffold, were selectively prepared upon reacting 2-carbamoylmethyl- or 2-ethoxycarbonylmethyl-3,4-dihydroisoquinolinium salts with hydrazine hydrate. Acylation of the primary amino group with benzoyl chlorides, followed by reductive ring cleavage of the annelated 4-imidazolidinone ring and final cyclodehydration of the N,N'-diacylhydrazines resulted in the synthesis of 1-methyl-2(5-aryl-[1,3,4]oxadiazol-2-ylmethyl)-1,2,3,4-tetrahydroisoquinolines which are of interest due to their potential use as bioisosteres of biologically active N-aryl-2-(1-methyl-3,4-dihydro-1H-isoquinolin-2-yl) acetamides

Fast polarization insensitive optical shutters using dual frequency liquid crystals

Most of the existing displays and optical shutters based on liquid crystals work in combination with linear polarizers. This implies that often more than half of the light is lost due to optical loss in the polarizers and/or the fact that the incoming light is unpolarized. For a number of shutter and filter applications it is important to have a high transmission, while it is not necessary to have a very high contrast. When considering nematic liquid crystals for use in fast optical shutters or filters, a number of possibilities exist. Dual-frequency liquid crystals offer faster switching possibilities because they can be switched from one state to another with a low frequency voltage and switching back can be achieved with the aid of a high frequency voltage. One of the limiting factors for the switching speed of dual-frequency nematics is the appearance of backflow. As in vertically aligned nematic devices, a certain threshold voltage exists above which the switching speed increases drastically [1]. Above the backflow threshold, the liquid crystal ends up in a meta-stable twisted orientation as shown in the figure below

The Cu(OTf)2 catalysed microwave assisted synthesis of a new scaffold, 7-aryl-7,8-dihydropyrido[4,3-c]pyridazin-5(6H)-one

The synthesis of novel 7-aryl-7,8-dihydropyrido[4,3-c]pyridazin-5(6H)-ones is described including a one-step Mannich-type reaction followed by intramolecular ring closure of ethyl 3-methylpyridazine-4- carboxylate and aldimines, catalysed by the Lewis acid Cu(OTf)2 under microwave heating. This synthesis opens up possibilities to access this unexplored scaffold for medicinal chemistry

Asymmetric synthesis of γ-chloro-α,β-diamino- and β,γ-aziridino-α-aminoacylpyrrolidines and -piperidines via stereoselective Mannich-type additions of N-(diphenylmethylene)glycinamides across α-chloro-N-sulfinylimines

The asymmetric synthesis of new chiral gamma-chloro-alpha,beta-diaminocarboxylamide derivatives by highly diastereoselective Mannich-type reactions of N-(diphenylmethylene) glycinamides across chiral alpha-chloro-N-p-toluenesulfinylaldimines was developed. The resulting (S-S,2S,3S)-gamma-chloro-alpha,beta-diaminocarboxylamides were formed with the opposite enantiotopic face selectivity as compared to the (S-S,2R,3R)-gamma-chloro-alpha,beta-diaminocarboxyl esters obtained via Mannich-type addition of analogous N-(diphenylmethylene) glycine esters across a chiral alpha-chloro-N-p-toluenesulfinylaldimine. Selective deprotection under different acidic reaction conditions and ring closure of the gamma-chloro-alpha,beta-diaminocarboxylamides was optimized, which resulted in N-alpha-deprotected syn-gamma-chloro-alpha,beta-diaminocarboxylamides, N-sulfinyl-beta,gamma-aziridino-alpha-aminocarboxylamide derivatives, a trans-imidazolidine, and an N-alpha,N-beta-deprotected syn-gamma-chloro-alpha,beta-diaminocarboxylamide