C−C Coupling Reactions of (Sulfene)ruthenium Complexes with Enolates

Schenk, Wolfdieter A.; Bezler, Jürgen

doi:10.1002/(sici)1099-0682(199805)1998:5<605::aid-ejic605>3.0.co;2-h

Cited by 7 publications

References 27 publications

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Chiral Ruthenium–Sulfene Complexes – Synthesis and C–C Coupling Reactions

Schenk¹,

Bezler²,

Burzlaff³

et al. 2000

Eur. J. Inorg. Chem.

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Reaction of the chiral racemic complex [CpRu(mppe)(SO2)]PF6 (1, mppe = Me2PC2H4PPh2) with diazomethane or ‐ethane gave the sulfene complexes [CpRu(mppe)(RHC/SO2)]PF6 (R = H, 2a; R = Me, 2b). Treatment of 2a with prochiral enamines or deprotonated β‐oxo esters yielded C–C coupling products with 32–60% de. An analog of 2a, [NmcpRu(mppe)(H2C/SO2)]PF6 (8, Nmcp = neomenthylcyclopentadienyl) was prepared in a four‐step synthesis starting from LiNmcp and [RuCl2(PPh3)3]. Repeated crystallization of the intermediate [NmcpRu(mppe)Cl] (6) provided diastereomerically pure 6′ which added methylene stereospecifically to give diastereomerically pure 8′. Compound 8 turned out to be much less reactive towards nucleophiles than 2a, but still added deprotonated ethyl 2‐methyl‐3‐oxobutanoate with 44% de. The chiral, enantiomerically pure sulfur dioxide complex [CpRu(chir)(SO2)]PF6 [10, chir = (S,S)‐Ph2PCHMeCHMePPh2] was synthesized from [CpRu(chir)Cl] and SO2 and was characterized by X‐ray crystallography. Reaction of 10 with diazomethane gave the enantiomerically pure sulfene complex [CpRu(chir)(H2C/SO2)]PF6 (11). Addition reactions of 11 with N‐(1‐cyclopentenyl)morpholine, as well as with various enolates derived from β‐oxo esters or 1,3‐diesters proceeded with high yields and 20–90% de. The structure of a diastereomerically pure addition product, [CpRu(chir)(SO2CH2C(Me){C(O)Me}{C(O)OtBu}] (13d′), was determined crystallographically and was shown to have (R) configuration at the quaternary carbon atom. After alkylation of one of the S/O functions, the sulfinate ligand was cleaved from the metal center by ligand substitution with acetonitrile, and the resulting acetonitrile complex 15 was converted back into 10 by treatment with SO2.

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Chiral Ruthenium–Sulfene Complexes – Synthesis and C–C Coupling Reactions

Schenk¹,

Bezler²,

Burzlaff³

et al. 2000

Eur. J. Inorg. Chem.

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Diastereoselective Protonation, Substitution and Addition Reactions at Pseudotetrahedral Rhenium Complexes

et al. 2010

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The chiral N,P ligand P(Me)(Ph)[8‐(2‐methylquinolinyl)] (3) was synthesized and separated into its enantiomers via diastereomeric palladium complexes. The reactions of 3 and (RP)‐3 with [CpRe(CO)(NO)(NCMe)]BF4 (7) gave thediastereomeric complexes [CpRe(CO)(NO){P(Me)(Ph)(C10H8N)}]BF4 [8 and (RRe,SP/SRe,SP)‐8], which, upon borohydride reduction, yielded the corresponding methyl complexes [CpRe(NO){P(Me)(Ph)(C10H8N)}(CH3)] [9 and (RRe,SP/SRe,SP)‐9]. Treatment of 9 with HBF4 under carefully controlled conditions gave the diastereomerically pure chelates [CpRe(NO){P(Me)(Ph)(C10H8N)}]BF4 [(RRe,SP/SRe,RP)‐10, (RRe,RP/SRe,SP)‐10 and (RRe,SP)‐10]. The chelate ring was opened with NaSH to produce the hydrosulfido complexes [CpRe(NO){P(Me)(Ph)(C10H8N)}(SH)] [(RRe,SP/SRe,RP)‐11, (RRe,RP/SRe,SP)‐11 and (RRe,SP)‐11]. Each step in this sequence proceeded with retention of configuration at rhenium. Complex 11 underwent acid‐promoted condensation with aldehydes to give thioaldehyde complexes [CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHR)]BF4 (12a–d, R = Ph, Me, 4‐C6H4OMe, C6F5). The addition of nucleophiles X– to 12a gave rhenium‐coordinated α‐chiral thiolate complexes [CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(X)}] (13a–e, X = acac, PhCH2S, EtS, tBuS, CN) with 42–89 % de. The thiolate can readily be cleaved from the rhenium complex by a methylation/chelate ring‐closure strategy. The stereochemistry of the entire reaction sequence was corroborated for each step by X‐ray crystallography.

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