cyclization

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cyclization

[‚sī·klə′zā·shən]
(organic chemistry)
Changing an open-chain hydrocarbon to a closed ring.
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The compound 1 was condensed with acetophenone, p-methoxyacetophenone or p-nitroacetophenone using piperidine as a catalyst in the presence of ethanol as a solvent afforded polyfunctionally substituted intermediate compound 18, which is anticipated to cyclize into 2,5-dihydro-2-imino-4-phenyl-5-(1-phenylethylidene)thiophene-3-carbonitrile derivatives 19a-c.
TABLE I ELECTRICAL PROPERTIES OF TYPICAL MATRIX RESINS|1~ Matrix Resins Dielectric Constant Loss Tangent Polyester 2.7 to 3.2 0.005 to 0.02 Epoxy 3.0 to 3.4 0.01 to 0.03 Cyanate ester 2.7 to 3.2 0.004 to 0.01 Polymide 2.7 to 3.2 0.005 to 0.007 Polyetherketone 3.1 0.004 Polybutadiene|4~ 2.2 0.0005 Epoxy-Anhydride-PBD 2.502 0.007 Since this system cures with a peroxide at 150|degrees~C, and thermally cyclizes at 240|degrees~C, plus or minus a few degrees, it has some built-in heat resistance.
Methadone is extensively metabolized by hydroxylation and dealkylation of the nitrogen methyl groups; these dealkylated metabolites are unstable and spontaneously cyclize to form 2-ethylene1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), which may further N-demethylate (1).
The amide intermediate then cyclize via internal nucleophilic attack by nitrogen is followed by elimination of water to give the target 3-isoindolo-2-yl-2-substituted quinazolin4(3H)-one (1-3) in substantial yield (Table-1)
This process results in much faster dehydrogenation reactions by removing the hydrogen atoms from methylene ([CH.sub.2]) groups while making more carbon atoms available to cyclize and consequently results in an increased carbon yield (21).
Poly(amic acid) groups can suffer three types of transformations upon heating: the group can cyclize itself to produce either an isoimide group, an imide group, or to regenerate an anhydride molecule.
The DPD is a very unstable compound that reacts with water and cyclizes to form several furanones, one of which is thought to be the precursor of AI-2 (SCHAUDER et al., 2001).
The deaminated product of kynuramine, which spontaneously cyclizes to 4-hydroxyquinoline, was measured fluorometrically at 320 nm excitation and 380 nm emission wavelengths with a plate reader (SpectraMax M5, Molecular Devices, Sunnyvale, CA, USA).
The [alpha]-keto acid spontaneously cyclizes to form enamine/imine tautomers; but at the naturally acidic pH of ink, the [alpha]-keto acid dominates.
In contrast, more than 99% of aldosterone cyclizes, with the alde- hyde group at carbon 18 reacting with the hydroxyl at carbon 11, forming a stable 11,18 hemiacetal.