Flash vacuum pyrolysis apparatus

In a modified flash-vacuum-pyrolysis apparatus (Otto Fritz company, Hofheim, Germany) the Na salt of l-methylbicyclo[2.2.1]heptan-7-one tosylhydrazone (1 g, 3.2 mmol) was added in small portions over 1 h to silylated silica gel (2 - 3 g) in a preheated (250 "C) pyrolysis flask at 1 x 10 4-10 3 Torr. The volatile products (47-68%) were collected in a cooled [N2(1)J flask and were separated by preparative GC (Car-bowax + KOH on Chromosorb W, 4.5 m, 60 °C). 

Wentrup and co-workers also studied the flash vacuum pyrolysis of isopropylidene (monosubstituted amino)methylenemalonates (84JOC-2772). The pyrolysis of isopropylidene phenylaminomethylenemalonates (1223) between 400 and 600°C under a pressure of 10 5-10 3 torr afforded 4-hydroxyquinolines (1226) in 57-66% yields. The intermediates (1224 and 1225) of the pyrolysis of isopropylidene phenylaminomethylenemalonates (1223) could be isolated at - 196°C on KBr or BaF2 windows in a special apparatus allowing direct IR spectroscopic examination of the pyrolysates... 

Scheme 1. General apparatus for flash vacuum pyrolysis and/or flow pyrolysis [10]...

The technique of flash vacuum pyrolysis (FVP) is now weU estabUshed as a clean and selective method for bringing about unimolecular thermal reactions. The apparatus required is relatively simple and inexpensive to construct (20147 C1150), and its use is now spreading beyond groups specializing in the technique and finding occasional routine use in target-directed synthesis. In this review, we have aimed to describe aU studies... 

Lagow et al. during these experiments in addition made the most important discovery, that polylithioalkanes prior to pyrolysis are stable in the gas phase for a short period of time. In this way for the first time mass spectra have been achieved of those compounds which have no observable vapor pressure below 650 °C even in the highest possible vacuum. A temperature of 1500 °C has been reached in less than three seconds by a special flash-vaporization apparatus, whereby e.g. dilithio-... 

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