References
- Nakada , M. and Kojima , E. 1998 . Tetrahedron Lett. , 39 : 313
- (Z)-4-t-butyldimethylsilyloxy-3-methyl-2-butenoate 2 was prepared as follows. 2: 1H NMR δ 7.64–7.66 (m, 4H), 7.37–7.39 (m, 6H), 5.64 (s, 3H), 4.86 (s, 2H), 3.56 (s, 3H), 2.07 (s, 3H), 1.07 (s, 9H); IR (neat, cm−1) 3072, 2956, 2860, 1720, 1430, 1230, 1152, 1112, 1060, 822, 742, 702; HRMS m/z (M+-H) calcd 367.1729, obsd 3671723.
- Corey , E. J. and Katzenellenbogen , J. A. 1969 . J. Am. Chem. Soc. , 91 : 1851
- The dibromide was immediately used for the next step after workup without purification.
- The stereochemistry of the tetrasubstituted alkenes was determined by 1H-NMR techniques (noe measurement) and comparison with authentic samples prepared by another procedure.
- Other bases were also examined. But the bromination was very slow in the case of pyridine, N, N-dimethylaniline and a considerable amount of the starting material remained even after the addition of excess base and bromine.
- It has been reported that the stereospecificity of bromine addition to alkenes is disturbed when solvents of high electronic constant are used. See Buckless, R.E.; Bader, J.; Thurmaier, R.J. J. Org. Chem. 1962, 27, 4523. Heublein, G. J. Prakt. Chem. 1966, [4]31, 84.; Buckless, R.E.; Bader, J.; Miller, J.L.; Thurmaier, R.J. J. Org. Chem. 1967, 32, 888.; Heublein, G.; Lauterbach, H. J. Prakt. Chem. 1969, 311, 91.; Ruasse, M.; Dubois, J. E. J. Am. Chem. Soc. 1975, 97, 1977.