Syntheses Using Diazoketones

Removal of Triphenylphosphine Oxide by Precipitation with Zinc Chloride in Polar Solvents

“…Lewis acid TPPO adducts are also well-known and have been used in the extraction of metal salts but have been less frequently applied to the removal of TPPO. For example, crystals of ZnCl 2 (TPPO) 2 have been known for over 100 years, yet we could only find one report where ZnCl 2 was used to precipitate TPPO from ethereal reaction mixtures and one patent where precipitation was mentioned, without examples, alongside more detailed methods using MgCl 2 . Although the magnesium chloride method has been utilized on scale, it is notable that a switch to a less polar solvent was required for efficient separation…”

.delta.-Dicarbonyl sugars. 5. A novel synthesis of a branched-chain cyclitol

“…The water layer was made acidic by treating it with an acid form cation-exchange resin (8 mL, amberlite IR-120 H+, 20-50 mesh), the resin was removed by filtration, and the filtrate was extracted with three 50-mL portions of chloroform. The combined chloroform extracts were concentrated to give a white solid, which, when recrystallized from ether, gave 13 Methyl Tri-0-acetyl-6-deoxy-6-diazo-DL-xy7o-5-hexulosonate (14). Sodium bicarbonate (0.40 g, 0.0054 mol) was slowly added to an aqueous solution (10 mL) of methyl hydrogen tri-O-acetylxylarate (13,1.75 g, 0.0054 mol).…”

“…The oil (1.5 g) was chromatographed on silica gel (75 g in a 25 X 370 mm column) with dichoromethane-ether, 4:1, as the eluent. The major component, Rf 0.75, was isolated in chromatographically pure form as a light yellow oil (0.80 g, 53%) and identified as methyl tri-O-acetyl-6deoxy-6-diazo-DL-xyio-5-hexulosonate (14): IR (neat) 2110 (C=N=N), 1740 (C=0), and 1640 cm"1 (N=N). l,7-Bisdiazoheptane-2,6-dione (15).…”

“…(1) removal of the bulky acetoxy groups from the molecule to see if these groups were responsible for a conformation favorable for cyclic product formation, and (2) changing the type of carbonyl group which was affected in the cyclization. The first modification was realized with 1,7 -bis(diazo)heptane-2,6-dione12 (15), while methyl tri-0-acetyl-6-deoxy-6-diazo-DL-rylo-5-hexulosonate (14) satisfied the structural requirement prescribed by the second modification. The preparation of 14 was accomplished in several steps beginning with the anhydride 3.…”

“…The methyl ester-diazo ketone 14, since it is structurally akin to 5, should be conformationally disposed to cyclize. The absence of cyclic products in the decomposition mixture from 14 may simply mean that the methyl ester carbonyl carbon is not electrophilic enough to react with the anionic portion of the ylide, a step that gives the carbocyclic ring. Instead, the ylide is preferentially converted to the final acyclic product 17.…”