Chromatographic silica

A solution of 3-oxatetracyclo[3.2.0.02 7.04 f,]heptane (941 mg, 10 mmol) in anhyd benzene (10 mL), that had been treated with basic alumina prior to the experiment, was heated in a sealed tube for 4 h at 100 C. After cooling, Et2G (10 mL) was added. The mixture was chromatographed (silica gel, 30 g, Et20/pentane 7 3) to yield benzene as the first fraction and 900 mg (95%) of product. After careful evaporation of the Et20/pentane mixture, the product was purified by distillation to give a light yellow oil. 

M f-BuLi in pentane (14.7 mL, 22 mmol) was added dropwise to a stirred solution of 8 (R = /-Bu 2.63 g, 10 mmol) in anhyd THF (40 mL) at — 80C under an argon atmosphere, and the mixture was stirred at — 80 C for 1 h. After the addition of sublimed sulfur powder (320 mg, 10 mmol), the mixture was allowed to warm to rt over a 2-h period with stirring, and then EtOH (10 mL) was added. The mixture was heated at 55 C with stirring for 2-4 h, poured into ice-water (lOOmL), and then the whole was extracted with Et20 (3 x lOOmL). The combined extract was washed with brine, dried (MgS04), and concentrated in vacuo, and the residue was chromatographed (silica gel, hexane) yield 0.54 g (25%). 

A stirred solution of 2,4,6-triphenyl-l,3-oxazinium perchlorate (3.06 g, 7.5mmol) in MeCN (100 mL) was treated with ethyl diazoacetate (1.80 mL, 17.2 mmol) followed by i-Pr2NEt (0.64 mL, 3.75 mmol). After ca. 30 min the theoretical amount of N2 had been evolved. The solution was stirred for 15 h, aq NaHC03 was added and the mixture was extracted with CHC13. The dried (K2C03) extract was concentrated and the residue was chromatographed (silica gel, benzene) yield 1.10 g (38%) mp 161 C. 

A solution of a l-(2-acyloxyphenyl)-2-azidoethanone 3 (10 mmol) in benzene (30 mL) was slowly treated with (EtO)jP (1.66 g, 10 mmol) at 5-10 C under N2. The mixture was stirred for 30 min and then heated under reflux fora specified time (see Table). The resulting solution was evaporated under reduced pressure and the residue was chromatographed (silica gel, EtOAc/hexane 1 1) to give the colorless product, which was recrystallized from Et20 (4a-c) or EtOAc/EUO (4d). 

Ethyl 1//-l,2-diazepine-l-carboxylate (0.50g, 3.1 mmol) in benzene (100 mL) was treated with Fe2(CO)9 (1.50 g, 4.1 mmol) and the mixture was vigorously agitated at 20 C under N2. The mixture was filtered, the filtrate was evaporated and the residue was chromatographed (silica gel, EtOAc/cyclohexane 2 3) to give the product, which was sublimed at 60°C/0.04Torr yellow crystals mp 115 C. (The yield was not reported.)... 

The sodium salt of tropone tosylhydrazone (14.8 g, 50 mmol) and dimethyl acetylenedicarboxylate (14.6 g, 100 mmol) in bis(2-methoxyethyl) ether (70 mL) was heated at 120 C for 15 min. The solution was poured into H20 and the mixture extracted with Et20. The extract was washed with H20, followed by brine, and dried (Na2S04). The solution was evaporated to yield the crystalline product (4.01 g), together with an oil. The latter was chromatographed (silica gel) to give additional product (0.405 g) total yield 4.415 g (34%) mp 153-154°C (cyclohexane). 

The benzodiazepine 2-oxide 11a (0.20 g, 1.25 mmol) in MeOH (5 mL) was treated with NaOMe (0.15 g, large excess) and the mixture was stirred at 20 C for 18 h and evaporated in vacuo. The residue was extracted with CH2C12. The extract was washed with H,0. dried (MgS04) and evaporated and the residue was chromatographed (silica gel, hexane/i-Pr20, 1 1) yield 0.143 g (66%) yellow prisms (i-Pr20) mp 85-86 C. 

The imine 13 (1.0-2.0 g) in benzene or CH2C12 (200-300 mL) was irradiated under N2 in an immersion apparatus equipped with a 400-W high-pressure Hg lamp and a Pyrex filter and cooled internally with running water. When TLC showed that all the starting material had been consumed (1 -3 h) the solvent was removed under reduced pressure and the residue was chromatographed (silica gel. CH2C12). 

The pyridinium salt 3 (0.427 g, 1.81 mmol) in H20 (1 L) was irradiated for 40 min with a high-pressure Hg lamp. The resulting solution was treated with 2M HC1 to pH 1 and then extracted with CHd3 under Nj. The extract was dried (MgS04) and evaporated in vacuo and the residue was chromatographed (silica gel) yield 0.157g (63%) mp 35-39 C. 

An ice-cold solution of a dia/atricydoheptene 1 (0.5-1.5 mmol) in McCN (300 mL) was irradiated with a 30-W low-pressure Hg lamp for 10-15 min. The solvent was removed under reduced pressure and the residue was chromatographed (silica gel. Et20/hexane 1 1) to give the yellow product, which was re-crystallized (i-Pr20). 

A solution of a dihydropyrimidinethione 3 (5 mmol) in THF (5mL) was added dropwise to a stirred suspension of NaH (0.12 g, 5 mmol) in THF and the mixture was stirred at 20 C for 16 h. then concentrated to ca. 1 mL under reduced pressure. Et20 (30 mL) and H20 (30 mL) were added and the aqueous layer was extracted with EtzO (3 x lOmL). The combined organic phases were dried and evaporated in vacuo. The residue was chromatographed (silica gel, hexane/Et20). 

A solution of a 4-azidoquinoline (0.5-0.6 g) and NaOMe (0.3 0.35 g, large excess) in a mixture of MeOH (75 mL) and dioxane (75 mL) was irradiated for 20-30 min with a 400-W high-pressure Hg lamp under N2. A further quantity of NaOMe (1.0-2.0 g) was added and the solution stirred at 20 C for 7-8 h and then concentrated in vacuo. The residue was treated with ice-water (30 mL) and the mixture was extracted with Et20. The extract was washed with sat. brine, dried and evaporated under reduced pressure. The residue was chromatographed (silica gel, Et20) to give the 3//-1,4-benzodiazepine as a yellow oil. 

Benzene-1,2-diamine (0.27 g, 2.5 mmol) and an aroylketene dithioacetal 10 (2.5 mmol) in xylene (20 mL) were refluxed for 24 h and the resulting solution was evaporated in vacuo. The residue was chromatographed (silica gel, 8% EtOAc/petroleum ether). 

A mixture of a 3-arylisoxazol-5(4//)-one 21, a benzene-1,2-diamine (10 mmol each) and HOAc (10 mL) was heated on a steam bath for 1 2h and then poured onto crushed ice. Neutralization with NH4OH, followed by extraction with CHC13 (3 x 50 mL), drying and concentrating under reduced pressure gave a residue which was chromatographed (silica gel, benzene, petroleum ether). 

A solution of a 4-cyclopropyl-l, 5-benzodiazepin-2-one4 (5.7 mmol) anti NCS orNBS (5.7 mmol) in CHC13 (50mL) was refluxed for 4h, cooled and evaporated under reduced pressure. The residue was chromatographed (silica gel) and recrystallized (Et20/benzene). 

A1C1, (0.8 g, 6 mmol) was added to a solution of the chloride 1 (1.6 g, 5.2 mmol) and a nitrile (6 mmol) in 1,2-dichlorobenzene and the mixture was heated at 120-130 C for 20 min. The mixture was cooled, made alkaline with dil aq NaOH and extracted with Et20. The solvents were removed by steam distillation and the residue was chromatographed (silica gel. EtOAc/petroleum ether 1 9) to give the yellow product (deep red if R = Ar). 

The solution of the thallium derivative 19 in MeCN was treated with KI (0.246 g, 1.5 mmol) in H,0 (1 mL) and the product was extracted into tt20. The extract was washed with H20, dried (MgS04) and chromatographed (silica gel, petroleum ether) to give 20c as pale-yellow plates [yield 0.037 g (80% based on unrecovered 4) mp 92-94 C (petroleum ether)], followed by starting material 4 (0.005 g, 17%). 

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