1,3-dithian-2-yl(trimethyl)silane

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

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

Procedure: According to a procedure described in Boger, D. L.; Brotherton, C. E. J Org Chem. 1984, 49, 4050-4055, to a solution of 2-trimethylsilyl-1, 3-dithiane (1.2 mL, 6.3 mmol) in dry THF (40 mL) at 0° C. was added n-butyllithium (4 mL of 1.6 M in hexanes). After 15 minutes at 0° C. and 20 minutes at 4 mL of 1.6 M ambient temperature, a solution of 2, 5-dimethoxytetrahydrofuran-3-carboxaldehyde (1.00 g, 6.00 mmol) in dry THF (10 mL) was added dropwise. After 17 hours at ambient temperature, the resultant mixture was treated with saturated aqueous NH4Cl (10 mL) and partitioned between EtOAc and H2O. The layers were separated and the aqueousueous phase extracted with EtOAc:hex (1:1) two times. The combined organic layers were washed with brine, dried over Na2SO4, and concentrated to afford a residue which was purified via flash column chromatograpy with 10% EtOAc/hex as eluant to yield 1.06g (70%) of a mixture of diastereomeric 2-(2,5-dimethoxy-tetrahydrofuran-3-yl-methylidene)-1, 3-dithiane as a yellow oil, which was used without any further purification. After 17 hours at ambient temperature partitioned between EtOAc and H2O The layers were separated the aqueousueous phase extracted with EtOAc The combined organic layers were washed with brine dried over Na2SO4 concentrated to afford a residue which was purified via flash column chromatograpy with 10% EtOAc/hex as eluant

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 28.8 g of 2-trimethylsilyl-1,3-dithiane were dissolved in 290 ml of peroxide-free tetrahydrofuran and the solution was treated dropwise at -60° C. with 93 ml of a 1.6M solution of n-butyl lithium in hexane. The mixture was left to warm to 0° C. within 3 hours and subsequently again cooled to -60° C. A solution of 24.87 g of 6-fluoro-4-chromanone in 150 ml of tetrahydrofuran was subsequently slowly added dropwise and the mixture was left to warm slowly from -60° C. to room temperature while stirring overnight. The mixture was subsequently poured into 2.5 l of water and extracted with four portions of ethyl acetate. The organic extracts were washed with saturated sodium chloride solution and dried with sodium sulfate The concentrated extract was decolorized with active carbon in a mixture of ether and low-boiling petroleum ether (1:1) and crystallized from the same mixture in the cold. After two recrystallizations, the combined mother liquors were chromatographed on a silica gel 60 column [hexane/ethyl acetate (9:1)]. The product-containing fractions were concentrated and the residue was recrystallized. There was obtained 4-m-dithian-2-ylidene-6-fluoro-2,3-dihydro-4H-1-benzopyran of melting point 47°-49° C. The mixture was left subsequently again cooled to -60° C the mixture was left to warm slowly from -60° C. to room temperature extracted with four portions of ethyl acetate The organic extracts were washed with saturated sodium chloride solution dried with sodium sulfate The concentrated extract was decolorized with active carbon in a mixture of ether and low-boiling petroleum ether (1:1) crystallized from the same mixture in the cold After two recrystallizations the combined mother liquors were chromatographed on a silica gel 60 column [hexane/ethyl acetate (9:1)] The product-containing fractions were concentrated the residue was recrystallized

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 28.8 g of 2-trimethylsilyl-1,3-dithiane were dissolved in 290 ml of peroxide-free tetrahydrofuran and the solution was treated dropwise at -60° C. with 93 ml of a 1.6M solution of n-butyl lithium in hexane. The mixture was left to warm to 0° C. within 3 hours and subsequently again cooled to -60° C. A solution of 24.87 g of 6-fluoro-4-chromanone in 150 ml of tetrahydrofuran was subsequently slowly added dropwise and the mixture was left to warm slowly from -60° C. to room temperature while stirring overnight. The mixture was subsequently poured into 2.5 l of water and extracted with four portions of ethyl acetate. The organic extracts were washed with saturated sodium chloride solution and dried with sodium sulfate The concentrated extract was decolorized with active carbon in a mixture of ether and low-boiling petroleum ether (1:1) and crystallized from the same mixture in the cold. After two recrystallizations, the combined mother liquors were chromatographed on a silica gel 60 column [hexane/ethyl acetate (9:1)]. The product-containing fractions were concentrated and the residue was recrystallized. There was obtained 4-m-dithian-2-ylidene-6-fluoro-2,3-dihydro-4H-1-benzopyran of melting point 47°-49° C. The mixture was left subsequently again cooled to -60° C the mixture was left to warm slowly from -60° C. to room temperature extracted with four portions of ethyl acetate The organic extracts were washed with saturated sodium chloride solution dried with sodium sulfate The concentrated extract was decolorized with active carbon in a mixture of ether and low-boiling petroleum ether (1:1) crystallized from the same mixture in the cold After two recrystallizations the combined mother liquors were chromatographed on a silica gel 60 column [hexane/ethyl acetate (9:1)] The product-containing fractions were concentrated the residue was recrystallized