PCC（Pyrindium Chlorochromate）

the solids suspended in the reaction andthe chromium species are removed by filtration through a pad of Florisil1,silica gel, alumina or Celite, and the pad is washed with an organic solvent,such as ether, DCM, or EtOAc. Sometimes, the solids can be removed bydecantation. Other times, it is advisable to add some diethyl ether to thereaction mixture before the filtration, in order to promote the separation ofreduced chromium species in a granular form. Occasionally, the reaction mixtureis concentrated before the addition of diethyl ether. Finally, the collectedorganic phases are concentrated at the rotary evaporator, giving a crudealdehyde or ketone that may need some further purification.

反应会实例

A 500-mL, round-bottomed flask equipped with a 4.5-cm, egg-shaped Teflon-coated magnetic stir bar ischarged with 130 mL of CH2Cl2, the alcohol prepared in Step A (10.4 g, 40.0 mmol), and 15 g of freshly powdered 3 Å molecularsieves. Pyridinium chlorochromate (21.5 g, 100mmol) is added portionwise over 10 min and the resulting mixture isstirred at room temperature for 15 hr. Ether (200 mL) is added slowly with vigorous stirring and thesolution is filtered under vacuum through a pad of 35 g of Celite. The solids remaining in the reactionflask are transferred to the Celite pad by scraping with a spatula and washing with three 50-mLportions of ether. The resulting cloudybrown filtrate is concentrated by rotary evaporation at room temperature togive a brown solid. To this solid is added 25 mL of 1:1 ether:hexaneand the solids are scraped with a spatula. The mixture is then poured onto 60 g of Whatman 60 Å (230-400 mesh) silicagel packed in a 4-cm diameter chromatography column and the liquid is adsorbedonto the silica gel by grity. The material remaining in the flask is furtherwashed with 1:1 ether:hexane and transferred ontothe silica gel; this process is repeated until all the material has been loadedonto the silica gel. The ketone is eluted using 500 mL of1:1 ether:hexane and the eluent is concentrated by rotaryevaporation to afford the crude ketone as a white solid. This material isdissolved in 40-45 mL of boiling hexane. Upon cooling the solution to room temperature,the ketone begins to crystallize. The flask is then cooled to −25 °C for 2 hr. The resulting solids arecollected by filtration, washed with three 25-mL portionsof cold (−25 °C) hexane, and dried to afford 8.84-9.08 g, (86-88%)of the ketone as a white solid.

Notes：PCC is prepared by addition of pyridine to a solution of chromium trioxide (CrO3)in aqueous HCland crystallization.

Reference:OrganicSyntheses, Vol. 80, p.1

【 Synlett 2004, 738–740】

参考文献

一、Name Reactions （A Collection of Detailed Reaction Mechanisms）, Jie Jack Li, PCC oxidation，page 336.

二、common oxidation reagents, Yue Xu, Sundia Meditech

三、药名标准操作

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