Pyrolysis levoglucosenone from

Scheme 3 Production of levoglucosenone from cellulose by pyrolysis...

TABLE II. YIELDS OF LEVOGLUCOSENONE FROM THE PYROLYSIS OF DIFFERENT MATERIALS AT 350° ... 

Levoglucosenone (287), readily available by the pyrolysis of cellulose, when heated with a variety of dienes in the absence of a Lewis acid provided exclusively products (289) resulting from cycloaddition to its convex face (Scheme 69, Table 15)7 ... 

Dehydration Reactions. Detailed analysis of the pyrolysis tar as discussed previously (Figure 12 and Scheme 3) shows the presence of levoglucosan, its furanose isomer (1,6-anhydro-p-D-glucofuranose) and their transglycosylation products as the main components. In addition to these compounds, the pyrolyzate contains minor amounts of a variety of products formed from dehydration of the glucose units. The dehydration products detected include 3-deoxy-o-erythrohexo-sulose, 5-hydroxymethyl-2-furaldehyde, 2-furaldehyde (furfural), other furan derivatives, levoglucosenone (l,6-anhydro-3,4-dideoxy-P-D-glycerohex-3-enopyranos-2-ulose), l,5-anhydro-4-deoxy-D-hex-l-ene-3-ulose, and other pyran derivatives. The dehydration products are important as intermediate compounds in char formation. 

The Yohimbe alkaloids such as alloyohimbane (1) and the antihypertensive drug reserpine constitute attractive goals for synthetic chemists. Syntheses of Yohimbe alkaloids from noncarbohydrates have been reported. " Synthesis of 1 from cellulose has also been achieved (Scheme 1). Pyrolysis of cellulose gave the levoglucosenone (l,6-anhydro-3,4-dideoxy- 3-D-glycero-hex-3-enopyrano-2-ulose, 2), which underwent Diels-Alder cycloaddition with... 

Opening of the anhydro-ring of 2,3,4-tri-C>-acetyl-l,6-anhydro-j3-D-gluco-pyranose with titanium tetrachloride and alkoxytitanium trichlorides has been examined. Data have been presented to show that l,6-anhydro-3,4-dideoxy-jS-D-5-/ycero-hex-3-enopyranos-2-ulose(levoglucosenone) is not principally derived from 1,6-anhydro-jS-D-glucopyranose on acid-catalysed pyrolysis of cellulose. It appears that l,6-anhydro-j8-D-glucopyranose itself is not a primary product of cellulose pyrolysis, so that the principal mechanism of its formation must involve a precursor still to be identified. 

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