Diols, oxidative lactonization

Chiral Alcohols and Lactones. HLAT) has been widely used for stereoselective oxidations of a variety of prochiral diols to lactones on a preparative scale. In most cases pro-(3) hydroxyl is oxidized irrespective of the substituents. The method is apphcable among others to tit-1,2-bis(hydroxymethyl) derivatives of cyclopropane, cyclobutane, cyclohexane, and cyclohexene. Resulting y-lactones are isolated in 68—90% yields and of 100% (164,165). 

D. After saponification of D to the corresponding diol, oxidation of the primary hydroxy group with tetra(n-propyl)ammonium perruthenate produced lactone... 

Hiroi et al. developed a new system for the oxidative lactonization of diols using acetone as cooxidant and catalyzed by the Cp lr complex bearing an... 

The latter were transformed into (+)-64, (-)-65 and (+)-66, respectively, in good yields. Lactone (+)-66 was also prepared in 37 % yield by stereospecific Horse Liver Alcohol Dehydrogenase (HLADH) catalyzed oxidation of the meso-diol 67. Lactones (-)-64 and (+)-64 are potentially interesting starting materials for the... 

Nakata showed that stoich. RuOyCCl oxidised steroidal diols to the corresponding ketones [237] electrogenerated RuO from RuO /aq. NaCl/Na(H3PO ) pH 4/ Pt electrodes converted diols to lactones and keto acids (Tables 2.1-2.4) [267] and RuCyaq. 10(0H)3/CC1 -CH3CN oxidised 3-(benzyloxy)-l,2-octanediol to the acid (Tables 3.4, 3.5) [107]. A diol was converted to a lactone by stoicheio-metric oxidation with RuOyCCl as part of the total synthesis of the quassinoid ( )-amarolide [82],... 

Typical examples are listed in Table 2.1. A few oxidations are effected by RuO but in general it is too powerful an oxidant for this purpose. The system RuCyaq. NaCl-CCy Pt anode oxidised benzyl alcohol to benzaldehyde and benzoic acid and p-anisaldehyde to p-anisic acid [24], and a wide range of primary alcohols and aldehydes were converted to carboxylic acids, secondary alcohols to ketones, l, -diols to lactones and keto acids from RuOj/aq. NaCl pH 4/Na(H3PO )/Pt electrodes (Tables 2.1-2.4). The system [RuO ] "/aq. K3(S303)/Adogen /CH3Cl3 oxidised benzyhc alcohols to aldehydes [30]. The oxidation catalyst TPAP (( Pr N)[RuO ]) (cf. 1.3.4) is extremely useful as an oxidant of primary alcohols to aldehydes and secondary alcohols to ketones without... 

A corollary of this selectivity is the very easy transformation of diols into lactones with silver carbonate on Celite .16 During the oxidation of a diol with Fetizon s reagent, as soon as an intermediate hydroxyaldehyde is able to equilibrate with a certain proportion of hemiacetal—even if present... 

As for oxidation reactions catalyzed by HLADH, the most frequently reported method is the coupling with FMN [222-224], It has been used for instance for the oxidation of many meso-diols forming lactones [250, 251], or for the oxidation of primary alcohols to obtain chiral aldehydes [252]. Generally, these syntheses were carried out at 12 g scale within a reaction time of a few hours up to 2-3 weeks [247],... 

Heterogeneous oxidation of diols to lactones.1 A mixture of KMn04 and Cu-S04-5H20 is recommended for heterogeneous oxidation of 1,4- and 1,5-diols to lactones. This oxidation can be highly selective since primary alcohols are oxidized... 

Reagent mixtures which utilize a catalytic metal complex, usually with a cooxidant (analogous to the Pt/02 reagent) for the selective oxidation of diols to lactones have been studied recently, with some interesting results. 

A thorough study of the use of HLADH for the enantioselective oxidation of mefo-diols to lactones has provided a venatile and synthetically useful route to enantiomerically enriched lactones. There are two major advantages of this system in that it appears to accept a ftdr amount of structural variatitm and full experimental details are available for preparative scale oxidatitms. A selection of results obtained with this enzyme system is presented in Scheme 14. 

Aliphatic alcohols are converted to a symme-RCOOCH2R) by oxidation with PCC on aluminum without solvent. Oxone in aqueous methanol also converts aryl aldehydes to the corresponding ester. Ally lie alcohols are converted to conjugated esters with Mn02, NaCN in methanol-acetic acid. Primary alcohols are oxidized to the methyl ester with tri-chloroisocyanuric acid in methanol. This reagent also converts diols to lactones. 

Because the conversion of primary diols into lactones is accomplished not only by oxidizing agents but also by catalytic dehydrogenation, it is likely that the reaction takes place stepwise via hemiacetal intermediates (equation 294) [355]. 

An early synthesis of lactacystin, not via the P-lactone, used glucose as starting material.20 Disconnection to 115 (the vinyl group can be converted into COzH and the benzyl ether into CHO) gives a structure that can be redrawn as 116 and then, with incorporation of an extra C atom (to be removed in the synthesis by diol oxidation) derived from 117. 

Trichloromelamine (TCM), because of the simple procedure, mild conditions, high selectivity, and low cost, is a useful reagent for the selective oxidation of alcohols to the corresponding carbonyl compounds. Oxidation of diols to lactones with two equivalents of TCM in dichloromethane is also reported. Lactones of five- and six-membered rings only were obtained in 87% and 95% yield respectively four- and seven-membered ring lactonization did not occur (Scheme 80) <93JOC5003>. 

Oxidation of alcohols. The oxidation of primary alcohols to aldehydes with aqueous NaBrO is catalyzed either by Cu or BujSnCl. a,[Pg.330]

Oxidations/hydroxylations of linactivated saturated carbons (polyunsaturated) fatty acids epoxidation and dihydroxylation of alkenes aromatic compounds (- unsaturated diols) hydroxylated compounds and aldehydes diols (and lactonization) enzyme catalyzed Baeyer-Villiger oxidations organic sulfides (sulfoxidation) Be, Mi, Mp, Po, Ra, CytP450 enzymes, monooxygenases SLO An, Nc, Po Pp (mutant strain), Ce Go, Ps Bp, Go, Ko, Ps, HLADH Ac, Ps, CHO BY, An, Ceq, Mi, Po, CPO, BSA... 

Lactones. A-Haloamides, including NCS, oxidize diols to lactones at room .emperature. However,the scope of this reaction has to be established further. 

Silylation of 276 with TBSOTf furnishes the bis-TBS ether, which undergoes an osmium tetroxide hydroxylation to afford the syn,anti,syn,anti,syn- iQi o 278 in 73% yield and with high diastereoselectivity. Selective diol oxidative cleavage with periodic acid, PCC oxidation of the resulting epimeric lactols to the lactone, followed by deprotection with /7-toluene-... 

Selective Oxidations. The selective oxidation of 1,4 and 1,5 primary-secondary diols to lactones is a valuable application of this reagent. Few general mild reagents for the chemoselec-tive oxidation to the hydroxy aldehyde are available. The most widely known reagents are Pt and O2, and Dihydridotetrakis-(triphenylphosphine)ruthenium(II) Hydroxy aldehydes, in their lactol form, are then oxidized further to lactones. The use of TPAP is advantageous in that it is commercially available, employs mild catalytic reaction conditions, and reacts with high selectivity in unsymmetrical cases (eq 8). Lactones have also heen formed from primary-tertiary diols. ... 

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