2-(Diethoxymethyl)furan

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Following the procedure for preparing 2-(diethoxymethyl)-5-(tributylstannyl)-thiophene as described in step (1) of Example 1, 17 g (10 mmol) of 2-(diethoxymethyl)furan was converted to 32.6 g (82% yield) of 2-(diethoxymethyl)-5-(tributylstannyl) furan (bp 110° C., 1 torr).

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 2-(diethoxymethyl)furan (2.00 g, 11.75 mmol) in dry THF (8 mL) was added a solution of n-BuLi (1.6 M in Hexane) (8.80 mL, 14.1 mmol) at −78° C. The resulting mixture was stirred at −78° C. for 1 h and treated with methyldisulfide (1.06 mL, 11.75 mmol). The reaction mixture was stirred at −78° C. for 30 min followed by warming to 0° C. for 1 hour. HCl (1N) (20 mL) was added and the organic material was extracted with ether (2×50 mL). The combined organic fractions were dried (MgSO4) and concentrated in vacuo to afford 1.58 g (94%) of crude title compound. LCMS (+ESI, M+H+) m/z 143. The reaction mixture was stirred at −78° C. for 30 min by warming to 0° C. for 1 hour the organic material was extracted with ether (2×50 mL) The combined organic fractions were dried (MgSO4) concentrated in vacuo

Conditions: temp:-65.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 20.88 g of chlorocyclohexane (0.176 mol) and 27.2 g of furfural diethyl acetal (0.16 mol) is added dropwise to a suspension of 2.35 g of lithium granules (0.34 mol) in 300 g of THF at −65° C., with an addition time of 2 hours being selected. After a conversion of the chlorocyclohexane of >97% determined by GC (total of 10 h), 18.3 g of trimethyl borate (0.176 mol) are added dropwise at the same temperature over a period of 30 minutes. After stirring for another 30 minutes at −65° C., the reaction mixture is poured into 120 g of water, the pH is adjusted to 6.3 by means of 37% HCl, and THF and cyclohexane are distilled off at a maximum of 35° C. under reduced pressure. The pH is subsequently adjusted to 1.5, the mixture is stirred until all the product has precipitated and the product is filtered off. After washing with a little cold water and a little cold acetone and drying, 17.2 g of 5-formyl-2-furanboronic acid (0.123 mol, 77%) are obtained in the form of a fine beige powders, HPLC purity >99% a/a. are added dropwise at the same temperature over a period of 30 minutes are distilled off at a maximum of 35° C. under reduced pressure the mixture is stirred until all the product has precipitated the product is filtered off After washing with a little cold water a little cold acetone and drying