The<unk>  is an organic synthesis in which a furan is converted to a dihydropyran. In the original publication by Osman<unk>  Jr. in 1971  furfuryl alcohol is reacted with bromine in methanol to  2,5-dimethoxy-2,5-dihydrofuran which rearranges to the dihydropyran with dilute sulfuric acid. Additional reaction steps, alcohol protection with methyl orthoformate and boron trifluoride) and ketone reduction with sodium borohydride produce an intermediate from which many monosaccharides can be synthesised.
The<unk>  protocol has been used in total synthesis for example that of desoxoprosophylline , Pyrenophorin  and Bao Gong Teng A . Very recently it has been used in diversity oriented synthesis  
and in enantiomeric scaffolding .
Achmatowicz reaction
Wolffenstein-Böters reaction
Wittig reaction
Doebner modification
Sabatier reaction
Chichibabin reaction
Bucherer-Bergs reaction
Flow birefringence