High sektivity to the corresponding ketones and atdehydea has heen obsavcd for the title readion when pafommi in 1.2-dichlaoerbane at 80Β°C ia the presence of catalytic amounts of pyridinium dicluomate and Adogen 464. The oxidaticn~ of anactivated alcohols was leas efkimt under these conditions.
The oxidation of the hydroxy group is commonly carried out using large amounts of heavy metals. 1 These procedures are usually very effective but they can cause problems with regard to product isolation and lead to quantities of poisonous residues. Environmental and economical constraints are incentives to develop catalytic alternatives using clean oxidants. The oxidation of alcohols by f-BuOOH in the presence of small amounts of various chromium compounds has been previously described. 24 Such Cr-catalyzed oxidations were much less effective when using 30% H&5 or s&urn perborate as a cheaper peroxide. Although sodium percarbonate (WC) can display similar reactivity to sodium perborate,' we have now investigated the properties of this inexpensive and stable crystalline compound as a substitut for t-BuOOH. Note that SPC is a perhydrate "[email protected] H202" and not a peroxy salt.* SPC! is extensively used in the detergent industry as a bleaching agent and begins to emerge as a useful reagent in organic synthesis, but not yet for alcohol oxidations.79-1'2
Here, we are pleased to record that SPC used in r;onjunction with suitable CrV1-and phase-transfercatalysts oxidizes efficiently various alcohols. A number of catalysts and solvents have been tested. Presently, the best conditions am the use of catalytic amounts of both pyridinium dichrornate (PDC) and Adogen 464ta in 1.2-dichloroethane at 80Β°C. As exemplified by the runs compiled in the Table, high conversions have been thus achieved from allylic and benzylic alcohols leading to carbonyl compounds with fair to high selectivities (runs 1. 2,511) even with a primary alcohol (runs 12-15). As shown from 1-indanof, the presence of both catalysts is clearly required to achieve an efficient oxidation (runs 3, 4). In contrast to the preceding results, a lower conversion was obtained from saturated alcohols (runs 16, 17).