Oxidation Collins

R. M. Heck, J. M. Chen, and M. E. Collins "Oxidation Catalyst for Cogeneration AppHcations— Regeneration of Commercial Catalyst," paper... 

In a prostaglandin synthesis a carbonyl group was protected as an oxime in which the hydroxyl group was protected against Collins oxidation by the phenylthiome-thyl-group. The phenylthiomethyl group is readily removed to give an oxime that is then cleaved to the carbonyl compound. ... 

Scheme 68. Reaction conditions i, UAIH4, ii, PhCH Cl- AmONa m-CPBA NaOMe-MeOH Collins oxidation iii, Li(+BuO)3AlH iv, Mel-NaH-PhH v, i N HCl-acetone CH2=CHCH2BrMg vi, Na-liq NH3 vii, m-CPBA, p-Ts0H-H20-PhH viii, Jones oxidation, CH2N2 ix, NaBHa x, PhCOCl, i-PrzNLi-THF, HOAc xi, Et3N-H20-MeOH, SOCI2, NH3.

An efficient general synthesis of a variety of 3(2i/)-furanones has been developed. Aldol condensation of aldehydes with the enolate derived from 3-methyl-3-(trimethylsiloxy)-2-butanone (183) followed by Collins oxidation afforded 1,3-diketones (184). Acid catalyzed cyclodehydration leads to the corresponding 3(2//)-furanones (185) (Scheme 43)... 

The amino aldehydes Boc-Ala-H, Boc-Leu-H, Boc-Phe-H, and Boc-Thr(Bzl)-H had a much higher enantiomeric purity when prepared by reduction of Weinreb amides compared to the identical aldehydes prepared by the Collins oxidation of the alcohols (Table 5). 1314-20 ... 

Collins oxidation is very cheap, but has the added experimental difficulty of having to work under anhydrous conditions. Although sometimes it lacks the selectivity of PDC or PCC, it can produce very good yields of aldehydes and ketones in uncomplicated substrates. 

General Procedure for Oxidation of Alcohols to Aldehydes and Ketones by Collins Oxidation... 

A detailed description of a Collins oxidation on a multigram scale is provided. 

Protecting groups, including very labile ones, withstand the action of Collins reagent. The very labile primary TMS ethers are transformed into the corresponding aldehydes.103 As secondary and tertiary TMS ethers resist the action of Collins reagent, a protocol involving per-silylation followed by Collins oxidation allows the selective oxidation of primary alcohols in the presence of secondary ones.104... 

Most functional groups resist Collins oxidation, including the oxidation-sensitive sulfides106 and thioacetals.103 Although Collins reagent can transform alkenes into enones" and alkynes into inones,107 these reactions are slower than the oxidation of alcohols into aldehydes or ketones. Therefore, alcohols can be usually oxidized with no interference from alkenes108 or alkynes.109... 

This fluorine-containing, oxidation-resistant alcohol is best oxidized by the Pfitzner-Moffatt reaction, using dichloroacetic acid as catalyst. Observe the use of toluene, instead of carcinogenic benzene, as solvent. A Swern oxidation was not reproducible, and caused substantial epimerization of the isobutyl side chain. Collins oxidation was successful, but ... 

A good yield in the oxidation of this hindered secondary alcohol was obtained employing the Pfitzner-Moffatt method, by using ortophosphoric acid as a strong acidic activator. Collins oxidation delivers only a 38% yield. 

---