The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

Teachers Describe Epistemologies of Science Instruction Through Q Methodology

Creating scientifically literate students is a common goal among educational stakeholders. An understanding of nature of science is an important component of scientific literacy in K‐12 science education. Q methodology was used to investigate the opinions of preservice and in‐service teachers on how they intend to teach or currently teach science. Q methodology is a measurement tool designed to capture personal beliefs. Participants included 40 preservice and in‐service elementary and secondary science teachers who sorted 40 self‐referential statements regarding science instruction. The results identified three epistemologies toward teaching science: A Changing World, My Beliefs, and Tried and True. Participants with the A Changing World epistemology believe evidence is reliable, scientific knowledge is generated in multiple ways, and science changes in light of new evidence. The My Beliefs epistemology reflects that scientific knowledge is subject to change due to embedded bias, science is affected by culture and religion, and evolution should not be taught in the classroom. The Tried and True epistemology views a scientific method as an exact method to prove science, believes experiments are crucial for scientific discoveries, absolute truth exists in scientific knowledge, and society and cultural factors can be eliminated from investigations. Implications for preservice teacher education programs and in‐service teacher professional development are addressed.     

Assay of human erythrocyte pyrimidine and deoxypyrimidine 5'-nucleotidase by isocratic reversed-phase high-performance liquid chromatography

We report a rapid and reproducible assay for activity of human erythrocyte pyrimidine 5'-nucleotidase and deoxypyrimidine 5'-nucleotidase. The nucleotides CMP, UMP, dUMP, dCMP or dTMP are individually incubated 30 min at 37 degrees C with erythrocyte hemolysate and 4 mM magnesium chloride in Tris, pH 7.5. Data are provided for standardization of the reaction with each substrate. Individual nucleoside products are assayed in less than 10 min by reversed-phase high-performance liquid chromatography at 280 nm with 0-14% methanol in 0.01 M potassium dihydrogen phosphate. This is the first report of a high-performance liquid chromatographic assay system which allows quantitation of the activity of pyrimidine 5'-nucleotidase isozymes using five individual pyrimidine and deoxypyrimidine nucleotides as the substrates.     

Self-chemical ionization of diethylzinc

The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd.     

Stereoselective synthesis of 3-hydroxyproline benzyl esters from N-protected beta-aminoaldehydes and benzyl diazoacetate

The synthesis of a series of 3-hydroxyproline benzyl esters from alpha-alkyl and alpha-alkoxy N-protected aminoaldehydes with benzyl diazoacetate is described. Aldehydes with alpha-alkyl substituents afforded prolines as a single diastereomer with a trans-cis relative configuration in 14-77%. An alpha-tert-butyldimethylsilyloxy aminoaldehyde afforded a proline as a single diastereomer with a trans-trans relative configuration in 37% yield.     

Stereoselective synthesis of tetrahydrofurans via formal [3+2]-cycloaddition of aldehydes and allylsilanes. Formal total synthesis of the muscarine alkaloids (-)-allomuscarine and (+)-epimuscarine

The stereoselective synthesis of tetrahydrofurans was achieved by formal [3+2]-cycloaddition of allyl and crotylsilanes with alpha-triethylsilyloxy aldehydes. The scope of the reaction was examined by using different alpha-substituted aldehydes and different substituents on the silicon. Tamao oxidation of the products resulted in formation of diols that are easily functionalized allowing an entry to natural products synthesis. The formal total synthesis of the muscarine alkaloids (-)-allomuscarine and (+)-epimuscarine was achieved.     

Stereoselective synthesis of 3-alkyl-2-aryltetrahydrofuran-4-ols: total synthesis of (+/-)-paulownin

A formal [3 + 2]-cycloaddition involving the Lewis acid mediated reaction of alpha-silyloxy aldehydes and styrenes to afford 3-alkyl-2-aryltetrahydrofuran-4-ols has been developed. This methodology was applied to the total synthesis of the naturally occurring furofuran lignan (+/-)-paulownin.     

Development of the Environmental Education Teaching Efficacy Belief Instrument

The increasing popularity of including environmental topics and issues in school curricula has created a need for effective environmental education teachers. One way to evaluate teacher effectiveness is through teacher efficacy, a belief measure that evaluates a teacher's perception that he/she can teach effectively. Research suggests that teachers’ instructional decisions are influenced by their beliefs, which are framed by their personal experiences. Because teacher efficacy is content specific, the purpose of this study was to develop a survey, the Environmental Education Teacher Efficacy Belief Instrument (EETEBI), to measure the teacher efficacy beliefs of preservice teachers as they relate to environmental education teaching strategies and outcomes.