1,1 - dipiperidine, oxidant

In 1968, Mukaiyama et al.70 discovered that magnesium alkoxides—generated by reaction of Grignard reagents with aldehydes—when treated in situ with l,r-(azodicarbonyl)dipiperidine (ADD) (69), suffer oxidation to the corresponding ketones. 

Another well-known process that utilizes a nucleophilic phosphane is the Mit-sunobu reaction, that is, the reaction between an acidic partner and an alcohol, typically facilitated by an azodicarboxylate and a phosphane. Two options are possible, anchoring of the electrophilic part to the solid support, dealt with in the next section, or anchoring of the nucleophilic phosphane. Georg et al. used polystyrene-bound triphenylphosphane and DEAD (diethyl azodicarboxylate) in their synthesis of aryl ethers [31]. Alcohols were reacted successfully with electron-rich and electron-deficient phenols, giving the desired products in good yield and purity. More recently, Wilhite and coworkers disclosed an efficient protocol for the synthesis of pyridine ethers using ADDP [l,l -(azodicarbonyl)dipiperidine] and polymer-supported triphenylphosphane (Scheme 6.9) [32], Both methods eliminate purification problems caused by triphenylphosphane oxide, but chromatography is still needed. 

Blau reported in 1898 that the saturated a,a -dipiperidine (36a) forms a purple iron(II) complex. This surprising finding was later shown by Krumhok " to be due to air oxidation of the ligand in the presence of to give the tris chelate of (36b). He also demonstrated the template reaction of methylamine with glyoxal or biacetyl in the presence of Fe + that affords red tris complexes of the diimines (37a) and (37b). Although the free ligands are unstable, these complexes are very stable with respect to dissociation in acid but rather less so towards alkali. Their visible spectra are similar to those of [Fe(bipy)3] " and [Fe(phen)3] ". For [Fe(37b)3], = 568 (e = 1.07 x 1(f) and as... 

OXIDATION, REAGENTS 1,1 -(Azodi-carbonyl)dipiperidine. Benzeneseleninic acid. Benzeneseleninic anhydride. Barium manganate. Bis 3-salicylidene-aminopropyl] aminecobalt(II). Bisltri-n-butyltin) oxide. /-Butyl hydroperoxide. /-Butyl hydroperoxide-Selenium dioxide. Caro s acid. Ceric ammonium sulfate. Chromic acid-3,5-Dimethyl-pyrazole. Chromic acid-Silica gel. 1,4-Diazabicyclo[2.2.2] octane-Bromine. 

The glycol-cleavage oxidation has been utilized in numerous synthetic works, for example, the total syntheses of dipiperidine alkaloids virgidivarine and virgiboidine [1348], total synthesis ofresolvinE2 [1349], synthesis of a-substituted oxazolochlorin aminals or acetals from mera-tetraaryldihydroxychlorins [1350], asymmetric synthesis of l-(2- and 3-haloalkyl)azetidin-2-ones [1351], synthesis of 2-hydroxy-1,4-oxazin-... 

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