Diallyl Sulfide Complexes of Chiral Iron and Ruthenium Lewis Acids:  Ylide Generation and Diastereoselective [2,3] Sigmatropic Rearrangements To Give Thiolate Complexes with New Carbon Stereocenters

Abstract

Reactions of the racemic iron diallyl sulfide complex [(η5-C5H5)Fe(CO)(PPh3)(S(CH2CHCH2)2)]+BF4 - and t-BuOK (CH2Cl2 or THF, −80 to −60 °C) give the thiolate complex (η5-C5H5)Fe(CO)(PPh3)(SCH(CHCH2)CH2CHCH2) (65−92%) as 77−68:23−32 mixtures of SS,RR/SR,RS Fe,S C diastereomers. Reactions of the enantiomerically pure ruthenium diallyl sulfide complexes [(η5-C5H5)Ru(S,S-chiraphos)(S(CH2CRCH2)2)]+PF6 - (5 +PF6 -; R = a, H; R = b, CH3) and t-BuOK (CH2Cl2, −98 °C) give the thiolate complexes (η5-C5H5)Ru(S,S-chiraphos)(SCH(CRCH2)CH2CRCH2) as 78:22 (8a, >99%) and 87:13 (8b, 97%) mixtures of chromatographically separable SSS/SSR P C ,P‘ C ‘,S C diastereomers. These transformations likely involve intermediate sulfur ylides as described in the title. Reactions of 8a,b with CH3I or PhCH2I and then NaI (acetone, reflux) give, via cationic methyl or benzyl sulfide complexes, enantiomerically enriched R‘SCH(CH2CRCH2)CRCH2 (R/R‘ = H/CH3, 75%; CH3/CH3, 71%; H/PhCH2 and CH3/PhCH2, >99%) and (η5-C5H5)Ru(S,S-chiraphos)(I) (6, ≥97%). Complex 6 is readily recycled to enantiomerically pure 5a,b +PF6 - (NH4 +PF6 -, CH3OH, S(CH2CRCH2)2; 94−97%).

Asymmetric Ylide Reactions: Epoxidation, Cyclopropanation, Aziridination, Olefination, and Rearrangement

“…When the BF 4 - salt of enantiomerically pure ( S )- 309b was used, the slightly higher diastereoselectivity was obtained compared to the TfO - salt of ( S , R )- 309b , ratio of ( S , S ):( S , R ) = 99.5:0.5. The stereochemical outcome can be rationalized in light of conformations D and E of the ylide intermediates (Scheme ) 135b. From favored conformation D , the ( SS , RR ) diastereomer was exclusively formed.…”

Synthesis and Oxidation of Ruthenium Allyl Thioether Complexes Bearing Phosphite and Phosphonite Coligands [1]

“…Occasionally the use of alkyl halides for this purpose may pose a problem since the strongly nucleophilic halide anion will substitute the weakly donating thioether ligand [11]. In our case, this sec ondary reaction was safely avoided by limiting the reaction time to the necessary minimum.…”

Synthesis of cyclopentadienyl ruthenium 4-pyridine and 2-pyrimidine thiolates and their bimetallic group VI metal carbonyls

“…Several reports concerning ruthenium thiolato complexes with phosphine ligands have been investigated [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The complexes CpRu(PPh 3 ) 2 SR have been made from CpRu(PPh 3 ) 2 Cl and thiolate anions [19,28].…”

“…The complexes CpRu(PPh 3 ) 2 SR have been made from CpRu(PPh 3 ) 2 Cl and thiolate anions [19,28]. Typically, these complexes undergo exchange reactions with CO, NOBF 4 , P(OR) 3 or bis(phosphine) (PP) ligands to give the corresponding substituted products CpRu(CO)(PPh 3 )SR, [CpRu(NO)(PPh 3 )SR]BF 4 , CpRu(P(OR) 3 ) 2 SR or CpRu(PP)SR [15][16][17][18][19]25,28]. The site of attack on the ruthenium thiolates in these reactions is found to be the Ru center.…”