TPAP and as Organic Oxidants

There are several reviews on the properties of TPAP as a catalytic oxidant in organic chemistry, [57, 59, 450, 458, 459, 478]. 

The commonest solvent for TPAP in organic oxidations is CH Clj (DCM), normally in conjunction with 4 A powdered molecular sieves (PMS) to remove water formed during the oxidation. Addition of CH3CN, as in many Ru-catalysed oxidations, makes reactions with TPAP/NMO more effective [59], and occasionally CH3CN is used as the only solvent [159]. Ionic liquids, e.g. [emim](PF )/PMS [479] and [bmim](BF )/PMS [480] have been used with TPAP/NMO. It has also been used in supercritical CO [457]. 

TRAP has been used as TPAP/NMO/PMS/CH Cl in many instances for the oxidation of primary alcohols to aldehydes, but TRAP/NMO/PMS/CH CN and TPAP/NMO/PMS/CH Cl -CHjCN are increasingly used (2.1.2 and Table 2.1). As TPAP/NMO/CH Cl /PMS it is more effective at oxidising primary than secondary alcohols a 1 1 mixture of Me(CH2)70H with Me(CH2)3CH(OH)(CH2)2Me gave 85% of Me(CH3)gCHO and 15% of Me(CH3)3CO(CH3)3Me [481]. 

Several natural products and pharmaceuticals have been made in which a TRAP-catalysed oxidation of a primary alcohol to aldehyde step occnrs, and these are listed in 2.1.3 abscisic acid, altohyrtin A, (+)-arisngacin A, 14-[2H]-arteether (Fig. 2.4), astrogorgin, avermectin-Bla (Fig. 2.6), (H-)-batzelladine A (Fig. 1.13), brevetoxin B, (+)-catharanthin, ( )-epibatidine, 2-epibotcinolide, (-)-7-epicylin-drospermopsin, ( )-epimaritidine, epothilone C, irisqninone (Fig. 2.3), gambieric 

There is a primary alcohol-to-aldehyde step in the synthesis of (+)-batzelladine A, and it was suggested that the oxidation of the primary alcohol (1) with TRAP/ NMO/PMS/CH Cl proceeds through an iminium-Ru alkoxide complex (2), rearranging as in (3)-(4) to give the aldehyde (5) (Fig. 1.13) [101] (a similar mechanism was proposed for the Ru-catalysed oxidative cyanation of tertiary amines [403] cf. 5.1.3.4, Fig. 5.3). 

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