Swern oxidation hydroxylation reactions

In this reaction, considerable nitration of the tosyl groups was observed. The bicycle 89 was obtained in better yield (36%) from 88 by reaction with trifluoroacetyl nitrate in DCM <1996JOC8897, 1998LJSP5831099>. Swern oxidation of the dihydroxy diazocine 90a led to the oxygen-bridged hydroxyl diazocine 91 by transannular hemi-ketalization (Scheme 16) <1996JOC8897>. 

Scheme 1). ° Hydrogenation of 13 in the presence of Raney nickel afforded the corresponding amine, which underwent ring expansion followed by complete protection to furnish lactam 14. Hydride reduction of 14 gave 15, which was followed by Swern oxidation to give 16. Mitsunobu reaction converted the axial hydroxyl group in 16 to the... 

Methyl-a-D-galactopyranoside (13) was used for the synthesis of suitable intermediates for the synthesis of (+)-pancratistatin (3) and (+)-narciclasine (9) (Scheme 1). Protection of the primary hydroxyl group in 13 as the TIPS ether followed by per-benzylation afforded 14, and then removal of the TIPS group followed by Swern oxidation afforded 15. Reaction of 15 with 16 gave a mixture of diastereomers 17, which underwent bromination with Ph3PBr2 to produce 18. Heating of 18 in dry pyridine afforded 19 as an and Z mixture in 75%... 

The additional carbon atom required for building the five-membered ring D is then added by means of methyl-magnesium bromide (16-4). The ester at future C15 is reduced to a carbinol by reaction with lithium aluminum hydride. Swern oxidation (dimethyl sulfoxide and oxalyl chloride) next serves to oxidize each of the two resulting hydroxyl groups to carbonyl functions (16-5). Dieckmann-like base-catalyzed condensation then closes the five-membered ring... 

The synthesis began with the treatment of 3,4-anhydro-l,2-0-isopropylidene-D-erythritol 90 with 2-alkyl-2-lithio-l,3-dithiane 92 to give 93 (Scheme 16). Reductive desulfurization of 93 and transacetalization of the resulting 94 by the following reaction sequence (1. acidic hydrolysis 2. protection of the primary hydroxyl group 3. ketalization and 4. basic hydrolysis) afforded the primary alcohol 95. The Swern oxidation of 95 yielded the aldehyde 96. 

Paterson and Perkins developed a synthesis of denticulatin B (285) and its isomer denticulatin A using a late-stage aldol reaction [90]. Denticulatin B is a marine natural product isolated from the mollusk Siphoneria dmticulata. Aldol coupling of ketone 282 and aldehyde 283 provided the syn aldol adduct 284 in 90% yield as a mixture of diastereomers, as shown in Scheme 2.31. Swern oxidation of the hydroxyl groups and deprotection and cyclization with HF-pyridine afforded denticulatin B in 20% overall yield over nine steps. 

Swern-type oxidation of the terminal hydroxyl group in this last intermediate affords an intermediate (53) that now ineorporates the aldehyde group required for building the Miehael aeeeptor function. Thus reaction of that compound with the ylide from ethyl 2-diethoxyphosphonoacetate adds two carhon atoms and yields the acryhc ester (54). 

Swem showed that the permanganate oxidation of oleic acid (245) was pH dependent. Earlier, Lapworth and Mottram oxidized oleic acid to 9,10-dihydroxy stearic acid, 246,344 jp essentially quantitative yield by what might be considered standard conditions for hydroxylation 0.1% oleic acid, no more than 1% KMnOq, short reaction time (5 min), slight excess of alkali and a reaction temperature of 0-10°C.344 Swern found that... 

The main applications of oxalyl chloride, as described in Chapter 4, are the formation of aryl isocyanates and chloroformates (by reactions with amines and hydroxylic substrates, respectively), and the formation of acyl chlorides from carboxylic acids under very mild conditions. Oxalyl chloride reacts with amides to give acyl isocyanates, and it is used with dimethyl sulfoxide as a mild reagent for the oxidation of alcohols (Swern-type oxidation). It is also used with N,N-dimethylformamide as a mild reagent for chlorination and formylation. Oxalyl chloride is widely used in commercial formulations of speciality polymers, antioxidants, photographic chemicals, X-ray contrasting agents, and chemiluminescent materials. Other physical properties are presented in Chapter 3. 

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