Borane-dimethylsulfide

B. (Z)-l-Iodo-l-heptene.2 A solution of 8.52 g of (112 mmol) of borane-dimethylsulfide complex (Note 13) in 100 mL of ether is added to a flame-dried, three-necked, 300-mL, round-bottomed flask equipped with stirbar, temperature probe, and N2 inlet. The solution is cooled to 5°C with an ice-bath. Cyclohexene (18.4 g, 224 mmol) (Note 14) is then added by syringe over 10 min while keeping the temperature below 15°C. The mixture is stirred at 5°C for 15 min. A white solid precipitates either towards the end of the addition or during the subsequent stirring period. The reaction mixture is allowed to warm to room temperature and is stirred for 1 hr. The non-homogeneous solution is cooled to 2-3°C... 

With this encouraging result from the model system, a gram quantity of the racemic sulfoxide 40 was prepared by oxidation of benzoxathiin 16 with mCPBA and a small amount of chiral sulfoxide (A)-40 with 94% ee was isolated by subsequent chiral HPLC separation (Scheme 5.12). When chiral sulfoxide (S)-40 was treated with borane-dimethylsulfide, a clean reduction of the olefin and the sulfoxide was observed. More surprisingly, only the desired cis-diaryl dihydrobenzoxathiin 12 was observed in high yield and unchanged 94% ee. No trans-isomer or 16 was observed. With this proof of concept in hand, an efficient... 

Reduction of sulfoxide (S)-40 was carried out in toluene using 1.05 equiv of 1M BH3-THF at 10°C, producing the cis-diaryl dihydrobenzoxathiin 12 with complete stereoselectivity. Upon work-up and crystallization from toluene and heptane, the desired product 12 was isolated in 88% yield and over 99% ee (Scheme 5.13). Borane dimethylsulfide led to a slower reaction. To the best of our knowledge, this synthetically useful reaction is unprecedented in the literature [13].1 Investigation... 

Tertiary amines have been prepared in good yield by a repetitive generation of imida-zolides and subsequent reduction with borane/dimethylsulfide, 1361 as the following examples show ... 

The Dean and Stark apparatus was removed, replaced by a condenser (the solution was flushed continuously with nitrogen) and the catalyst dissolved in anhydrous toluene (2 mL). Borane-dimethylsulfide (0.5 mL of a 2 M solution in tetrahydrofuran) was added to the mixture, which was heated to 110 °C. 

The flask was charged with the sulfoximine catalyst (68 mg) and dry toluene (4mL). To this white suspension was added borane dimethylsulfide (1.2 mL). The mixture became clear with the evolution of hydrogen. 

The temperature has a significant effect on the selectivity of the reaction, with the optimal temperature being dependent on the borane source. The optimal range of temperature was 25 °C when borane-dimethylsulfide was used and 0-5 °C when borane-tetrahydrofuran was used as the reducing agent (Table 11.5). 

M Borane-dimethylsulfide complex (2.0 mL) was added to the resulting solution. The mixture was cooled to 0-5 °C with an ice-bath, and then a solution of 2,3-butadione monoxime trityl ether (1.72 g) in dry tetrahydrofuran (5 mL) was added dropwise via a syringe pump over 1 hour at that temperature. 

Compound with 9S-cinchonan-9-ol (3974950-3), 67, 1 Borane-dimethylsulfide (13292-87-0), 68, 77 Borane, tetrahydrofuran complex, 69, 214... 

SYNTHESIS A solution of 5.50 g 2,5-dimethoxy-4-ethylthio-B-nitrostyrene (see under 2C-T-2 for its preparation) was made in 80 mL boiling anhydrous THF. On cooling, there was some separation of a fine crystalline phase, which was kept dispersed by continuous stirring. Under an inert atmosphere there was added 3.5 mL of a 10 M borane dimethylsulfide complex, followed by 0.5 g sodium borohydride as a solid. There was a slight exothermic response, and the color slowly faded. Stirring was continued for a week. There was then added 40 mL H,0 and 20 mL... 

Hydroboration-oxidation of enecarbamates with borane-dimethylsulfide complex gives reasonable yields of /i-hydn > xycarbarn ales (equation 28) with some diastereoselectivity, depending upon what other functional groups are present in the starting material152. 

Radical methods are useful for the synthesis of highly functionalized enantiomerically pure cyclopentane derivatives [95SL918]. Reductive cyclization of the arabinolactone 88 furnished the eir-lactone 89 in quantitative yield. Exhaustive reduction with borane-dimethylsulfide gave the functionalized cyclopentane 90. 

In the case of H-CBS, this catalyst could be prepared by mixing diphenylprolinol with borane-THF (tetrahydrofuran) or borane dimethylsulfide. Despite numerous efforts in many groups to isolate or even characterize H-CBS by nuclear magnetic resonance spectroscopy, all attempts have been unsuccessful. H-CBS is used in situ, and good results can be obtained in many cases. 

Borane complexes, borane-THF and borane dimethylsulfide, are generally the appropriate reducing agents in this reaction. Borane thioxane has been used, but it suffers from the inconvenience that thioxane is quite expensive. Diborane gas has been tried by Callery and has proved to be very efficient. The use of this reagent could open new industrial developments for this technology. Catecholborane has shown some advantages at low temperature when selectivity is needed.40... 

To a suspension of 2-(8-carbamoylmethyl-6/7,12/7-5,ll-methano-dibenzo[Z>/ [l,5]diazocin-2-yl)acetamide 29 (0.155 g, 0.461 mmol) in THF (6.00 mL) under N2 at 0 °C was added borane-dimethylsulfide (BH3.DMS) complex (0.700 mL, 7.38 mmol) and reaction was refluxed at 80 °C for 29 h. The reaction was allowed to come to room temperature followed by addition of MeOH/HCl (3.00 mL) the reaction was refluxed for an additional 30 min. The reaction was cooled to room temperature and the volatile components were removed under reduced pressure. The residue was taken up in H20 (5.00 mL) and basified to pH = 11.5. This mixture was extracted with CH2C12 (3 x 30 mL), washed with brine, dried over Na2SC>4, and filtered. The volatile components were removed under reduced pressure and the crude product was purified by flash column chromatography on silica gel [CHCI3 MeOH NH4OH (100 40 1) to give 0.139 g of 30 as a white solid in 98 % yield. 

The benzoyl groups of 43 were reduced using a borane-dimethylsulfide complex to give the corresponding iV-benzy 1 -diazocinc 44, which, upon hydrogenolysis with 20% Pd(OH)2 followed by acid hydrolysis, afforded the NH diazocine 30 (R = H) (Scheme 10) <1998CPB674>. 

Treatment of cyanoethylcellulose with borane-dimethylsulfide or borane-tetrahydrofuran complexes in tetrahydrofuran has resulted in the quantitative conversion to 3-aminopropylceIlulose. Such aminopropylcellulose derivatives have also been employed as intermediates for acetamido or aryluredo products, and in grafting reactions [119]. 

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