Pyridine sulfur trioxide complex

Sulfur trioxide pyridine complex [26412-87-3] M 159.2, m 155-165°, 175°. Wash the solid with a little CCI4 then H2O to remove traces of pyridine sulfate, and dry over P2O5 [Chem Ber 59 1166 1926 Synthesis 59 1979]. 

The use of dimethyl sulfoxide-acetic anhydride as a reagent for the oxidation of unhindered steroidal alcohols does not appear to be as promising due to extensive formation of by-products. However, the reagent is sufficiently reactive to oxidize the hindered 11 j -hydroxyl group to the 11-ketone in moderate yield. The use of sulfur trioxide-pyridine complex in dimethyl sulfoxide has also been reported. The results parallel those using DCC-DMSO but reaction times are much shorter and the work-up is more facile since the separation of dicyclohexylurea is not necessary. Allylic alcohols can be oxidized by this procedure without significant side reactions. 

Pyridinium-1-sulfonate was prepared according to the procedure of Sisler and Audrieth. The submitter reports that this procedure may be conveniently carried out at 5 times the specified scale. The reagent should be dry and used soon after its preparation. The checkers found that a technical grade of pyridinium-1-sulfonate (sulfur trioxide pyridine complex) purchased from Aldrich Chemical Company, Inc., gave substantially lower yields of product. 

Although the most characteristic reaction of the pyrrole nucleus is the predominant addition of electrophiles to the C-2 position, it is interesting to note that contrary to previous assumptions, sulfonation of pyrrole and its 1-methyl derivative with sulfur trioxide-pyridine complex affords mainly the 3-sulfonated pyrroles <00TL6605>. As Mizuno wisely points out, it is likely that some of the pyrrole-2-sulfonates reported previously are actually pyrrole-3-sulfonates. 

Interesting selectivity has been observed with some substituted carbohydrates. On treatment with sulfur trioxide-pyridine complex in A/,A/-dimethylformamide, methyl 4,6-O-benzylidene-a-D-... 

A total of 10.0 g (8.9 mmol) SASRIN resin2 (note 1) was washed with N,N-dimethyIfonnamide (DMF 2 x 25 mL), methanol (MeOH 2 x 25 mL), and dichloromethane (DCM note 2 2 x 25 mL), and dried under vacuum (0.5 torr) at 70°C overnight. To a suspension of the dried SASRIN resin in lOOmL of methyl sulfoxide (DMSO note 2) and 25 mL of DCM was added 12.4 mL (89 mmol, 10.0 Eq.) triethylamine (note 2) followed by 7.1 g (44.5 mmol, 5.0 Eq.) sulfur trioxide-pyridine complex (note 2). The suspension was shaken on a radial arm at room temperature overnight (note 3) filtered on a glass frit and washed with DCM (3 x 100mL), DMSO (3 x lOOmL), DCM (3 x lOOmL), and tetrahydrofuran (THF 3 x 100 mL) and dried under vacuum (0.5 torr) at room temperature to give 10.0 g Ameba resin (notes 4 and 5). 

DCM (anhydrous), DMSO (anhydrous), triethylamine (99 + %), sulfur trioxide-pyridine complex, DMA (anhydrous), potassium tert-butoxide (95%), DCE (anhydrous), 2-(4-methoxyphenyl)ethylamine (98 + %), sodium triacetoxy-borohydride (95%), A/A-diisopropylethylamine (99%), p-toluenesulfonyl chloride (99 + %), and trifluoroacetic acid (99 + %) were obtained from Aldrich Chemical Company, Inc. 4-Hydroxy-2-methoxybenzaldehyde (>98%) was obtained from Fluka Chemie, AG. 

Methacycline Methacycline, 4-dimethylamino-l,4,4a,5,5a,6,ll,12a-octahydro-3,6,10, 12,12a-pentahydroxy-6-methylen-l,ll-dioxo-2-naphthacencarboxamide (32.3.6), is synthesized from oxytetracycline (32.3.2), which is reacted with a sulfur trioxide— pyridine complex, resulting in an oxidation reaction. Simultaneous sulfonation gives a naphthacen-snlfotetrahydrofuran derivative intermediate (32.3.5), which when reacted with hydrofluoric acid forms methacycline (32.3.6) [222-225]. 

Furan is resinified by sulfuric acid but it can be sulfonated with the complex of sulfur trioxide with pyridine or dioxane. Depending on conditions the 2-sulfonic or the 2,5-disulfonic acid may be obtained. Furan-2-carboxylic acid can be sulfonated with oleum. Benzo[6]furan is polymerized by sulfuric acid. The 2-sulfonic acid has been obtained by oxidation of the sulfinic acid available in turn by treatment of the lithio derivative with sulfur dioxide. Benzo[6]furan with the sulfur trioxide-pyridine complex allegedly affords the 3-sulfonic acid. 

Sulfonation of selenophene with the sulfur trioxide-pyridine complex occurs at the 2-position the 2-sulfonic acid is conveniently isolated as its barium salt (64JGU1814). 

Silyl ethers of aliphatic alcohols are inert towards strong bases, oxidants (ozone [81], Dess-Martin periodinane [605], iodonium salts [610,611], sulfur trioxide-pyridine complex [398]), and weak acids (e.g., 1 mol/L HC02H in DCM [605]), but can be selectively cleaved by treatment with HF in pyridine or with TBAF (Table 3.32). Phenols can also be linked to insoluble supports as silyl ethers, but these are less stable than alkyl silyl ethers and can even be cleaved by treatment with acyl halides under basic reaction conditions [595], Silyl ether attachment has been successfully used for the solid-phase synthesis of oligosaccharides [600,601,612,613] and peptides [614]. 

Sulfonation of pyrrole and its 1-methyl derivative with a sulfur trioxide-pyridine complex was found (by chemical and NMR experiments) to give 3-sulfonated pyrroles 420 (Scheme 89) <2000TL6605>, but not 2-sulfonates as described... 

The above discussion has concentrated upon the reagents used, but it is equally of value to comment on the substrate, particularly in reactions for which other oxidation methods have been reported to fail. A good example is the oxidation of the iron-carbonyl complex (31) to the ketone (32 equation 14). The use of dimethyl sulfoxide activated with sulfur trioxide-pyridine complex gave a 70% yield of the product, in contrast to the use of the Pfitzner-Moffatt procedure (dimethyl sulfoxide-DCC) or the chromium... 

A second entry to dicarbonyl substrates utilizes the aldol reaction to establish the a-methyl center prior to oxidation of the p-hydroxyl moiety. Commonly, this oxidation is performed using the Sulfur Trioxide-Pyridine complex, which results in <1% epimerization of the methyl-bearing center (eq 34). Interestingly, this procedure procures the opposite methyl stereochemistry from that obtained through enolate acylation of the same enantiomer of oxazolidinone. 

Goh and Harvey effected the oxidation of the m-diol (3) to the o-quinone (4) efficiently by use of the sulfur trioxide-pyridine complex in DMSO-triethylamine. Use of DMSO-acetic anhydride (I, 305 2, 163-165 3,121-122) gave fair, but erratic yields of the quinones. Other reagents were completely unsuccessful. Note that oxidation... 

Compound 22 was prepared by oxidation of P-amino alcohol 21 that was readily derived from Z-cysteine as shown in Fig (9). Although the oxidation of 21 by Swem oxidation proceeds in 81% yield, it requires cryogenic conditions as low as -bO C. In order to eliminate the impractical reaction conditions, an oxidation using sulfur trioxide pyridine complex (S03-py) [77] was examined (Table 1). Treatment of... 

Sulfonation was carried out by heating the asphalt with sulfur trioxide-trimethyl amine complex or sulfur trioxide-pyridine complex at temperatures near 135°C. Sulfamic acid treatment was also included in this series. Many other reagents were evaluated such as methyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid, 2-dimethyl-aminoethyl methacrylate, 2-vinylpyridine, 4-vinylpyridine, tetrahydro-phthalic anhydride, norbomene dicarboxylic anhydride, and phthalic anhydride. 

Typical procedure. l,5-Dimethyl-4-methoxycyclohexa-2,4-dienylacetaldehyde 1884 [1399, 1401] To a solution of 2-(l,5-dimethyl-4-methoxycyclohexa-2,4-dienyl)ethanol (450 mg, 2.47 mmol) in anhydrous triethylamine (5 mL) and anhydrous dimethyl sulfoxide (5 mL) was added a solution of sulfur trioxide-pyridine complex (1.90 g,... 

In this reaction, the sulfur trioxide-pyridine complex adds to the carbonyl group of the aliphatic aldehyde to yield the 1-alkyl-1-(1-proto-l-pyridyl)-l-methanesulfate derivative 81. 

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