Furan → 8-Oxabicyclo[3.2.1]oct-6-en-3-one

Beteiligte Stoffe

Reaktionsschritte

8-Oxa-bicyclo[3.2.1]oct-6-en-3-one was synthesized by the known [4+3] cycloaddition of the commercially available furan and the oxyally generated from 1,1,3-trichloroacetone, followed by reduction with zinc (J. Org. Chem. 1999, 64, 3398 and J. Am. Chem. Soc. 2001, 123, 5590). Internal double bond of the cycloadduct was reduced using Pd/C in MeOH to give 8-oxa-bicyclo[3.2.1]octan-3-one. The resulting ketone was subjected to Eadsworth-Horner-Emmons condition to yield the α,β-unsatured ester. Catalytic hydrogenation of the conjugated ester gave rise to an inseparable mixture (˜1:1) of diasteromers with no diastereoselectivity. The mixture of diastereomers carried forward to the next two steps. These steps include reduction of esters with NaBH4/LiCl followed by treatment with TsCl in the presence of NEt3 to furnish the oxabicyclo[3.2.1]octaneethylmethylbenzensolfonate. 1H NMR (CDCl3): δ 7.81-7.78 (m, 2H), 7.37-7.34 (m, 2H), 4.35-4.28 (m, 2H), 4.07-4.02 (m, 2H), 2.46 (s, 3H), 2.07 (m, 1H), 1.95-1.87 (m, 2H), 1.82-1.76 (m, 1H), 1.68-1.63 (m, 2H), 1.55-1.50 (m, 2H), 1.43-1.28 (m, 2H), 1.10 (m, 1H).

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