Dodecylbenzenesulfonyl

Fig. 13 Synthesis of oxazoles on JandaJel. Reagents and conditions a toluene, alkyl acetoacetate (R0(C0)CH2C0R R =t-Bu), reflux, 6h or alkyl acetoacetate (R = Me, Et), toluene, LiC104, reflux, 6h fc dodecylbenzenesulfonyl azide, EtsN, toluene, rt, 16 h c benzamide, Rh2(oct)4, toluene, 65 °C, Ih rf Burgess reagent, pyridine, chlorobenzene, MW 100 °C, 15 min (or 80 °C, 4 h with conventional heating) e AICI3, piperidine, CH2CI2, rt, 16 h...

In the same context, Muller et al. have reported the reaction of ethyl 3,3, 3-trifluoro-2-diazopropionate with various olefins catalysed by dirhodium tet-rakis[(i )-(A/-dodecylbenzenesulfonyl)prolinate], Rh2[(f )-DOSP]4. Yields and... 

Rhodium(II) (iV-dodecylbenzenesulfonyl)prolinate has been found to act as an effective catalyst for the enantioselective decomposition of vinyldiazoacetates to c -divinylcyclopropanes. Combination of this process with a subsequent Cope rearrangement has resulted in a highly enantioselective synthesis of a variety of cycloheptadienes containing multiple stereogenic centres (see Scheme 40). The tandem... 

Commercially available p-acetamidobenzenesulfonyl azide (Aldrich Chemical Company, Inc.) was preferred over p-dodecylbenzenesulfonyl azide (Danheiser, R. L Miller, R. F. Brisbois, Org. Synth. 1995, 73, 134, Note 9 Ref. 4a), or methanesulfonyl azide4 for reasons of safety, yield, and ease of manipulation. 

The submitters originally used methanesulfonyl azide,4 but the Board of Editors of Organic Syntheses requested substitution of the much less shock sensitive reagent 4-dodecylbenzenesulfonyl azide. The use of methanesulfonyl azide has previously been recommended,43 since excess reagent as well as certain formamide by-products can be easily separated from the desired diazo ketone product during workup by extraction into dilute aqueous base. 

When 4-dodecylbenzenesulfonyl azide is used for the diazo transfer reaction, the crude reaction product is contaminated with by-products that cannot be separated during basic workup, and consequently column chromatography is required lor the purification of the diazo ketone. Use of mesyl azide for the diazo transfer reaction allows purification of the crude reaction product by recrystallization from diethyl ether-pentane to obtain 10.11 g (86%) of the desired diazo ketone. 

Caution Although the mixture of dodecylbenzenesulfonyl azides is the safest of a group of diazo transfer reagents,2 one should keep in mind the inherent instability, shock sensitivity, and explosive power of azides. All users should exercise appropriate caution. 

Plpet 5 mL of the hexane solution containing 4-dodecylbenzenesulfonyl azides into a 100-mL volumetric flask and dilute to the mark with methanol. Pipet 5 mL of this solution Into a small stoppered flask. Add 2 mL of aqueous t N potassium hydroxide solution and heat at 75°C for 20 min. Allow to cool to room temperature, add 2 drops of 0.1% phenolphthalein solution, and 10 mL of 1.5% Na2S04. Shake, then transfer quantitatively to a 60-mL separatory funnel. Add 10 mL of butanol (or isoamyl alcohol) to the sample flask, shake, then transfer to the separatory funnel. Shake the funnel, let the layers separate, then remove the bottom (H2O) layer into a 100-mL volumetric flask, Add an additional 10 mL of 1.5% Na2SC>4 to the alcohol layer in the separatory funnel, shake, let the layers separate, then transfer the water layer to the volumetric flask. Neutralize the lined water layers to the phenolphthalein endpoint with 1 N hydrochloric acid, then immediately add 25 mL of Fe(NH4)(S04>2. Dilute to the mark with 1.5% Na2S04 solution, let stand 10 min, then read absorbance at 458 nm. Read azide concentration against the NaN3 calibration curve. 

Dodecylbenzenesulfonyl chlorides have been prepared from the corresponding acids using chlorosulfonic acid,4 phosphorus oxychloride,2 and thionyl chloride.5 The use of catalytic amounts of DMF in conjunction with thionyl chloride is based on the work of H. Bosshard, et al. The insolubility of the DMF/thionyl chloride complex in the reaction solvent permits easy removal at the end of reaction. Extraction with dilute base removes the last trace of acids and the solution is pure enough for the next step. 

The method described above for the preparation of the mixture of 4-dodecylbenzenesulfonyl azides is new and based on the work of Bollinger and Hazen.5 7 Sulfonyl azides have been prepared by diazotizing substituted sulfonyl hydrazides,8 and treating sulfonyl halides in methanol-water,9 ethanol-water,10 acetone,2 5 7 or acetone-water solutions11 with aqueous or solid sodium azide,5 7 12 Use of phase transfer catalysis for the preparation of sulfonyl azides is new, simple and effective, ft avoids solvent changes and permits isolation of a hexane solution of sulfonyl azides without concentration. 

Dodecylbenzenesulfonyl azide was purchased by the checkers from TCI Americas Inc. and was used as received. 

Of the various rhodium(II) carboxylates [Rh2(OCOR )4, R =chiral residue] currently available, those based on -substituted L-prohne (Fig. 1) are among the most efficient in enantioselective cyclopropanation. Introduced by McKervey and co-workers [6,9] for intramolecular diazocarbonyl reactions, the N-benzenesulfonyl prohnate, Rh2(2S-BSP)4 (3), has been recently developed by Davies et al. [10,12] to the point where the J -fert-butylbenzenesulfonyl and N-dodecylbenzenesulfonyl derivatives, Rh2(2S-TBSP)4 and Rh2(2S-DOSP)4 (Fig. 

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