Chiral racemic rhenium thiolate complexes [CpRe-SCH 2 CH 2 NHAc (8), SCH 2 CH 2 C(O)OH (9). A milder synthesis using hydrated sodium carbonate as a base (NO)(PPh 3 )(SR)] were obtained under either acidic or basic conditions. Thus, when [CpRe(NO)(PPh 3 )(CH 3 )] (1) was provided 8 and compounds with SR = SCH 2 CH 2 C(O)OMe (10), SCH 2 CH 2 C(O)NHCH 2 Ph (11) in high yields. Using treated with etheral HBF 4 and HSR the thiolate complexes
similar methods, thiolate complexes of (R)-N-acetylcysteine (13), its methyl ester ( 14), (R)-N-phthaloylcysteine ( 16), and (O)OEt (3)] were obtained after chromatographic workup. Ligand exchange reactions between [CpRe(NO)(PPh 3 )-N-[(S)-3-mercapto-2-methylpropionyl]-S-proline (Captopril) (17) were obtained as diastereomeric pairs. The formation of (OC 4 H 8 )]BF 4 (4) and sodium thiolates yielded analogous complexes with SR = SH (5), SCH 2 CH 2 Ph (6), SCH 2 CH=CH 2 13 was preceded by the O-bonded isomer 12 which slowly rearranges in solution. 13 can be converted under acidic (7). SR groups which tolerate strongly alkaline conditions may be introduced by treatment of 4 with HSR in the conditions into its methyl ( 14) or ethyl (15) esters. The diastereomers of 16 were separated by crystallization, and presence of sodium ethoxide as demonstrated by the highyield synthesis of 2 as well as of complexes with SR = the structure of the (R,R)-isomer 16a determined.
Achiral Thiolates
rial. Although 4 was noted to be labile [14] it has found only Two synthetic strategies were chosen in which the rhesporadic use in ligand exchange reactions. [15] When 4 was nium-sulfur bond is formed under either acidic [8] or basic treated with isolated sodium thiolates in THF/ethanol, the