Carbon dioxide extrusion

Photolytic nitrogen extrusion from tetrazoline derivatives (283) and (284) permits further syntheses of diaziridin-ones (285a) and -imines (285b) respectively (75AG(E)428). Thermal carbon dioxide extrusion from a five-membered precursor can also give a diaziridinimine (75JOC3112). 

Pyrones behave as dienes and react with bismaleimides giving biscycload-ducts [62-65]. By heating, carbon dioxide extrusion takes place with formation of bisdienes. This reaction was used to prepare a polyimide with a bicyclooctene structure [51] (Fig. 15). 

The pyrrolooxazines (70) undergo Diels-Alder cycloadditions with AvV-diethyl-1 -propynylamine, followed by carbon dioxide extrusion to yield pyrrolopyridines (71) <87CB1427>. The furooxazines react similarly (Equation (24)). 

Similarly, flash-vacuum pyrolysis of 3-methyleneisobenzofuran-l (3/7)-one (4) and 3-methylene-benzofuran-3(2//)-one (5) at above 900°C afforded 2//-indene-l,3-dione and benzofuran, respectively carbon dioxide extrusion to methylenebenzocyclopropene did not occur. 

Nitrogen- and Oxygen-containing Rings - a-Hydroxy-hydroxamic acids react with carbonyl di-imidazole to give, after carbon dioxide extrusion either spontaneously or on heating, the substituted oxazetidin-3-ones (69), and 1,3-di-imines react with hydroxylamine in pyridine at room temperature to give the dihydroisoxazoles (70). 56... 

Yates and White (1989) introduced carboxylic acid functionality into PPE by metalation in solution with alkyl lithium and treatment with carbon dioxide. Extrusion of this functionalized PPE (45 parts) with PA-66 (45 parts) and SEES (10 parts) provided a composition which showed eightfold improvement in impact strength compared to a similar blend made with unfunctionalized PPE. 

Diels-Alder reaction foUowed by photochemical carbon dioxide extrusion (via acetal diradical and acetal carbene) provided a vosatile route to trisubstituted cyclohexenes 53 (Scheme 15).2 ... 

In an interesting reaction, pyrrolysis of the urethane leads to extrusion of carbon dioxide and formation of 23, propiomazine Although this agent contains the ethylenediamine side chain, its main use is as a sedative. 

Whereas electronically activated 2-pyrones can react thermally in both normal and inverse electron-demand Diels-Alder cycloaddition, 2-pyrone by itself requires thermal conditions that are so vigorous that they cause spontaneous extrusion of carbon dioxide from the bicyclic cycloadduct [61]. 

We use variants of profile extrusion to produce tubing -with diameters of less then 1 mm and pipes with diameters exceeding 1 m, Wall thicknesses can vary from a few tens of micrometers up to several centimeters. Extruded window and door frames are more complex than pipes. Such profiles are largely hollow with internal ribs and fins that reinforce and divide the interior into two or more channels. We use solid rubber profiles in applications such as door seals and windshield wipers. We can produce foamed extrudates by incorporating a blowing agent, such as butane or carbon dioxide, into the polymer in the molten state. As the polymer exits the die, its internal pressure drops and the dissolved gas expands to form bubbles within the product. Examples of foamed extrudates include pipe insulation and automobile door gaskets. 

Phenylsydnone 89 is not restricted to [3+2] cycloaddition. Reaction of sydnone 89 and its derivatives with the substituted azete 90 gives isomeric l//-triazepines after extrusion of carbon dioxide (Equation 8). 

The carbanion generated from deprotonation of the w-carbon atom of sulpholene reacts with aldehydes and ketones to give alcohols. Sulphur dioxide extrusion from the products results in (E)-a-hydroxy-l,3-dienes (equation 72), or dehydration followed by thermal desulphonylation results in trienes117. Dienones can be obtained if the initial condensation is conducted with an aldehyde, followed by oxidation and sulphur dioxide removal117. 

Nair and coworkers have described the [8 + 2] cycloaddition reactions of 2H-cyclohep-ta[fr]furan-2-ones such as 521 in several reports311. The reactions of 521 with alkenes yield azulene derivatives upon extrusion of carbon dioxide. Table 30 summarizes the results of the reactions between 521 and some 6,6-disubstituted fulvenes 522 (equation 151)311b. In the case of 6,6-dialkyl fulvenes 522a-c, the [8 + 2] cycloadducts 523 were the major adducts obtained, the Diels-Alder adducts 524 only being formed in trace amounts. 

The most probable mechanism for the reduction requires the initial nucleophilic attack by the hydridometal complex on the nitro group, followed by intramolecular cyclization and extrusion of carbon dioxide. Repetition of the cyclization and extrusion sequence, followed by proton transfer, leads to aniline (Scheme 11.6). 

The mesoionic compound prepared from L-Pro (83TL1067) reacts with acetylenic compounds to give pyrrolo[l,2-a]pyrazoles after extrusion of carbon dioxide ( Scheme 47). With phenylpropiolic acid, the natural product withasomnine (a) was formed in low yield (7%) together with its regioisomer (b, 5%) (85TL5739). 

In analogy with 143d, the 2-phenyl compound is obtained from tropone and 3-phenylsydnone in a low yield [93JCS(P1)1617]. The cycloaddition proceeds peri- and regioselectively in a [4it + 2tt] mode followed by extrusion of carbon dioxide from the primary adduct and spontaneous dehydrogenation. 

Blends of poly (ethylene terephthalate) (PETP) and polypropylene (PP) with different rheological properties were dry blended or compounded, and extrusion foamed using both physical blowing and chemical agents, and the foam properties compared with those of foam produced from the individual components in the absence of compatibilisers and rheology modifiers. The foams were characterised by measurement of density, cell size and thermal properties. Low density foam with a fine cell size was obtained by addition of a compatibiliser and a co-agent, and foamed using carbon dioxide. The presence of PP or a polyolefin-based compatibiliser did not effect... 

Details are given of the development of an on-line sensor using near IR spectroscoy for monitoring carbon dioxide concentration in polymeric extrusion foaming processes. The calibration curve relating the absorbance spectrum at 2019 nm to the dissolved gas concentration was derived so as to infer dissolved carbon dioxide gas concentration... 

EFFECT OF TALC ON CELL NUCLEATION IN EXTRUSION FOAM PROCESSING OF POLYPROPYLENE WITH CARBON DIOXIDE AND ISOPENTANE... 

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