35930-31-5

Upstream product

• 186581-53-3 diazomethane 
• 4670-29-5 5-Hydroxy-2,8,8-trimethyl-8H-pyrano<2,3-h>chromone 
• 25983-76-0 isoevodionol 
• 141-78-6 ethyl acetate 
• 77-78-1 dimethyl sulfate 
• 83805-66-7 7-(1,1-dimethyl-2-propynyloxy)-8-iodo-5-methoxy-2-methyl-4H-1-benzopyran-4-one 
• 39548-89-5 1-(4-(benzyloxy)-2-hydroxy-6-methoxyphenyl)ethan-1-one 
• 32550-59-7 6-Acetyl-5-hydroxy-7-methoxy-3,4-dihydro-2,2-dimethyl-2H<1>benzopyran 
• 126444-80-2 6-Acetyl-5-acetyloxy-7-methoxy-2,2-dimethyl-2H-chroman 
• 126444-81-3 1-(5-Hydroxy-7-methoxy-2,2-dimethyl-chroman-6-yl)-butane-1,3-dione 
• 13476-24-9 Isoheteropeucenin 
• 24128-11-8 6-Acetyl-5,7-dihydroxy-3,4-dihydro-2,2-dimethyl-2H-<1>benzopyran 
• 83805-61-2 1-(4-benzyloxy-2-hydroxy-6-methoxyphenyl)-1,3-butanedione 
• 83805-64-5 7-hydroxy-8-iodo-5-methoxy-2-methyl-4H-1-benzopyran-4-one 

Downstream Products

• 4670-29-5 5-Hydroxy-2,8,8-trimethyl-8H-pyrano<2,3-h>chromone 

Relevant academic research and scientific papers

Synthesis of methylisospatheliachromene, alloptaeroxylin and alloptaeroxylin methyl ether

6-Acetyl-7-acetyloxy-(II)-, 8-acetyl-7-acetyloxy-5-methoxy-(VII)- and 6-acetyl-5-acetyloxy-7-methoxy-(XII)-2,2-dimethyl-2H-chromans, derived from the corresponding acetylhydroxychromans(I), (VI) and (XI), on Baker-Venkataraman rearrangement with KOH-pyridine yield the β-diketones (III), (VIII) and (XIII) respectively.These on acid-catalysed cyclisation followed by dehydrogenation, afford the corresponding 2,2-dimethyl-2H-pyranochromones (V), (X) and (XV).Alloptaeroxylin methyl ether (XV) on demethylation with (AlCl3-CH3CN) yields alloptaeroxylin (XVI).

Synthesis of 3,4-Dihydro-2,2-dimethyl-2H-pyrano-chromones & 2,2-Dimethyl-2H-pyranochromones

Claisen condensation of 6-acetyl-7-hydroxy-(I), 8-acetyl-7-hydroxy-5-methoxy-(II), 6-acetyl-5-hydroxy-7-methoxy-(III) and 6-acetyl-7-hydroxy-5-methoxy-(IV)-2,2-dimethylchromans with ethyl acetate and sodium gives the corresponding 3,4-dihydro-2,2-dimethyl-2H-pyranochromones (V), (VI), (VII) and (VIII) respectively.V, VI and VII were dehydrogenated using (i) DDQ in benzene and (ii) NBS-Pyridine to give IX, X and XI respectively.Also, the chromenes obtained by the DDQ dehydrogenation of I, II and III on reaction with ethyl acetate and sodium , gave IX, X and XI respectively.

A New Synthesis of Alloptaeroxylin, Its Methyl Ether and Related Compounds

Claisen condensation of 6-acetyl-5,7-dihydroxy-2,2-dimethylchroman (I) with sodium and ethyl acetate gives isoheteropeucenin (II) and isopeucenin (III).Benzylic bromination of II and III with NBS followed by dehydrobromination with pyridine affords alloptaeroxylin (IV) and dehydroisopeucenin (V) respectively.IV on methylation gives alloptaeroxylin methyl ether (VI).VI has also been synthesized by an alternate route.

A Convenient Synthesis of Linear 2-Methylpyranochromones

A convenient synthesis of linear 2-methylpyranochromones, viz., spatheliachromen(5-hydroxy-2,2,8-trimethyl-2H,6H-benzodipyran-6-one), O-methylspatheliachromen (5-methoxy-2,2,8-trimethyl-2H,6H-benzodipyran-6-one) (8) and O-methylallopteroxylin (5-methoxy-2,8,8-trimethyl-4H,8H-benzodipyran-4-one> is described by blocking the eighth position of the corresponding 7-propargyl ether derivative 7-(1,1-dimethyl-2-propynyloxy)-8-iodo-5-methoxy-2-methyl-4H-1-benzopyran-4-one with iodine followed by thermal cyclization.The linear pyranochromones 2,2,8-trimethyl-2H,6H-benzodipyran-6-one and 8 are also synthesized starting with the easily available appropriate 3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-7-ols following the steps of Claisen condensation with ethyl acetate, cyclization with ethanolic sulfuric acid followed by dehydrogenation with NBS.

New Chromones from Cneoraceae

From Neochamaelea pulverulenta and Cneorum tricoccon the new and old chromones 1, 2, 4, 6, 8, 10, 11, 13, 18, 20, and 24 have been isolated.Syntheses of the natural (18, 20) and synthetic chromones (29, 30, and 34 - 39) are described.