Microwave thermolysis

Expeditious preparation of N-sulfonylimines has been optimized for one-pot solventless operation that involves microwave thermolysis of aldehydes and sulfonamides in presence of relatively benign reagents, calcium carbonate and montmoril-lonite K 10 clay (Scheme 6.23) [76],... 

Meshram, H.M., Ganesh, Y.S.S., Sekhar, K.C. and Yadav, J.S., Microwave thermolysis VII selective diversity in the reduction using sodium hypophosphite under microwave irradiation, Synlett, 2000, 993-994. 

Photodegradation [182] and microwave thermolysis [183] of pollutants, toxic agents or pathogens in waste water, often in combination with a solid catalyst (e.g., Ti02), are two important methods for their removal. Results from environmentally relevant studies of the combined use of MW and UV [97, 101-103] have already appeared in the scientific literature and the topic is also covered by several... 

Flash vacuum thermolysis (FVP) at 600°C or microwave excitation of 1-substituted perhydropyrido[l,2-f][l,3]oxa-zines afforded 1-substituted 1,4,5,6-tetrahydropyridines <2005TL5451>. Perhydropyrido[l,2-f][l,3]oxazin-l-ones were hydrolyzed with 2M ethanolic KOH to 2-(2-hydroxyalkyl)piperidines <1996CJC2434, 2005EJ01378>. (+)-9- />z -6-Epipinidinol 102 was similarly obtained from 3,8-dimethylperhydropyrido[l,2-f][l,3]oxazin-l-one 101 (Equation 16) <1998T13505>. 

Uncatalyzed amidations of acids have been realized under solvent-free conditions and with a very important microwave effect [67 a]. The best results were obtained by use of a slight excess of either amine or acid (1.5 equiv.). The reaction involves thermolysis of the previously formed ammonium salt (acid-base equilibrium) and is promoted by nucleophilic attack of the amine on the carbonyl moiety of the acid and removal of water at high temperature. The large difference in yields (MW > A) might be a consequence of interaction of the polar TS with the electric field (Eq. (15 a) and Tab. 3.6). 

Retro Diels-Alder reactions often require severe conditions, high temperatures, and, sometimes, flash vacuum thermolysis. Microwave irradiation has been used as an alternative to these harsh conditions [12], even using graphite as a support [45]. Similarly, the use of higher input power has enabled retro-Diels-Alder reactions of anthracene derivatives to occur in 3-5 min [41]. This method is an alternative to the use of flash thermolysis. The use of graphite is a prerequisite for obtaining high temperatures in a short time. 

Bortolussi described the synthesis of unsaturated amino alcohols 83 by thermolysis of furan adducts 82 use of microwaves resulted in a significant reduction in reaction time (Scheme 9.24) [75],... 

The reaction of C60 with o-quinonemethide, prepared from o-hydroxybenzyl alcohol (110) (Scheme 9.32), was performed in a modified domestic oven at 800 W and gave 111 in 27% yield after only 4 min [72], Although Eguchi et al. [83] reported the same reaction with a slightly better yield (31%) by thermolysis in a sealed vessel, the microwave approach to this adduct has the advantage of simplicity, and avoids the risks associated with high-pressure conditions. 

Since the early 2000s, different sources of CO have been explored and applied to carbonylation reactions for laboratory organic synthesis. For example, the use a stoichiometric amount of metal-carbonyl complexes, thermolysis of formic acid at high temperature, and the use of aldehydes via decarbonylation have been investigated. For the use of metal-carbonyl complexes and formaldehyde as carbonyl source, it has been shown that microwave irradiation greatly accelerates the process. ... 

Microwave-assisted thermolysis has also been applied to the unusually stable oxathiazolone 69. In this case, appreciable amounts of the adduct 72 were obtained only by microwave irradiation of oxathiazolone 69 at 200 °C for 10 min (Scheme 7) <2006CAR41>. 

The effects of increased temperature (thermolysis) of starch by conventional heating have been reviewed.2 In the present article, the effects of freezing, as well as heating by infrared and microwave radiations, are described. 

Numerous unsuccessful attempts to synthesize cyclopropanethione have been reported. Thermal or photochemical generation of the C3H4S species from different sources always leads to allene episulfide. Some representative experiments include (a) in vacuo pyrolysis of the sodium salt of 2,2,4,4-tetramethylthietanone tosylhydrazone (4) into the stable tetramethylallene episulfide (S), (b) pyrolytic extrusion of nitrogen from perfluorinated thiadiazoline 6, (c) in vacuo pyrolysis of spiro compound 8 into methylenethiirane (3), (d) the flash vacuum pyrolysis-microwave spectroscopic approach applied to spiro compounds 9 and 10, (e) pyrolysis of anthracene adduct 11 and tosylhydrazide salt 12, (f) thermolytic nitrogen extrusion from pyrazoline-4-thione 13, thermolysis of tetramethylallene episulfide (5) or pyrazoline 13 in dig-lyme solution, and photolytic nitrogen extrusion from pyrazoline 13, ° (g) thionation of methylenecyclopropanone 15, and (h) reaction of donor-acceptor substituted allenes 18 with elemental sulfur. ... 

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