Insights into the conversion of propargylic tosylates into bromoallenes

Synlett

Volumn , Issue 20, 2009, Pages 3303-3306

  Jian, Ya Jun ^a   Wu, Yikang ^a  

^a SHANGHAI INSTITUTE OF ORGANIC CHEMISTRY   (China)

Author keywords

Alkynes; Allenes; Bromine; Stereoselective synthesis; Substitutions

Indexed keywords

1 BROMOALLENE DERIVATIVE; ALLENE DERIVATIVE; COPPER; TOLUENESULFONIC ACID DERIVATIVE; UNCLASSIFIED DRUG;

ARTICLE; PHOTOCHEMISTRY; REACTION ANALYSIS; STEREOCHEMISTRY; SUBSTITUTION REACTION; SYNTHESIS;

EID: 72149111127     PISSN: 09365214     EISSN: 14372096     Source Type: Journal    
DOI: 10.1055/s-0029-1218378     Document Type: Article

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28. Unlike CuBr, CuBr2 is almost insoluble in Et2O or THF. The fluctuating results might be caused by the heterogeneity of such reaction system.
29. Their syntheses are given in Supporting Information.
30. General Procedure for the Conversion of Propargylic Tosylates into the Corresponding Bromoallenes To commercially available anhyd Et2O (7.0 mL) were added in turn CuBr (2.0 mmol), LiBr (1.0 mmol), and Cu(OTf)2 (0.1 mmol). The mixture was stirred at ambient temperature 15 min. To this purple solution was added a solution of the propargylic tosylate (i.e., 7 or 10, 1.0 mmol) in Et2O (3.0 mL). The mixture was then stirred at ambient temperature for 6 h before being diluted with Et2O, washed with aq sat. NH4Cl, H2O, and brine, and dried over anhyd Na2SO4. Removal of the drying agent by filtration and the solvent by rotary evaporation left the crude product oil, on which 1H NMR was run to determine the 8/9 (or 11/12) molar ratios. Column chromatography on silica gel gave 8/9 (or 11/12, in most cases almost inseparable from each other) for calculation of the yields. After removal of the protecting groups (e.g., the TBS in 8) the ee values could be determined by chiral HPLC.