in tetrahydrofuran Rh complex and Br2C(COOMe)2 in 1:1 molar ratio were heated in THF at 50°C for 2.3 h under N2; solvent was removed, residue extd. with hexane to give (MeOOC)2C=C(COOMe)2, which was recrystd. from CH2Cl2/EtOH, the extraction residue was chromd. (eluent CHCl3) to give RhBr(CO)(PPh3)2;

in tetrahydrofuran byproducts: carbon monoxide; mixture was stirred at -20°C for 15 h under CO; chromd. (alumina), recrystd. from CHCl3/EtOH;

in tetrahydrofuran byproducts: carbon monoxide; mixture was stirred at -20°C for 16 h under CO; chromd. (alumina), recrystd. from CHCl3/EtOH;

in tetrahydrofuran a suspn. of Rh complex in THF and MeCHCHCH2Br in 1:2 molar ratio sealedin vacuo in a Pyrex reaction tube was either stirred or shaken for 1 h at 20°C; volatiles were removed under vac., trapped at -196°C and analyzed by GLC, residue was chromd. using hexane followed by benzene or CHCl3 as eluent, and recrystd. from a mixt. of either CHCl3 and EtOH or benzene and MeOH;

in benzene room temp., 0.5 h; isolated yield after recrystn.; react. monitored with (1)H-NMR;

in tetrahydrofuran a suspn. of Rh complex in THF and CH2CHCH2Br in 1:2 molar ratio sealed in vacuo in a Pyrex reaction tube was either stirred or shaken for 1 h at 20°C; reaction was monitored by IR spectroscopy; volatiles were removed under vac., trapped at -196°C and analyzed by GLC, residue was chromd. using hexane followed by benzene or CHCl3 as eluent, and recrystd. from a mixt. of either CHCl3 and EtOH or benzene and MeOH;

in tetrahydrofuran a suspn. of Rh complex in THF and PhCH2Br in 1:2 molar ratio sealed in vacuo in a Pyrex reaction tube was either stirred or shaken for 4 h at 20°C; volatiles were removed under vac., trapped at -196°C and analyzed by GLC, residue was chromd. using hexane followed by benzene or CHCl3 as eluent, and recrystd. from a mixt. of either CHCl3 and EtOH or benzene and MeOH;

in tetrahydrofuran Rh complex and Br2C(COOMe)2 in 1:2 molar ratio were heated in THF at 50°C for 3.3 h under N2; solvent was removed, residue extd. with hexane to give (MeOOC)2C=C(COOMe)2, which was recrystd. from CH2Cl2/EtOH, the extraction residue was chromd. (eluent CHCl3) to give RhBr(CO)(PPh3)2;

1: methanol; acetone 2: methanol View Scheme

1: methanol; acetone 2: methanol View Scheme