Tetrahydrothiophene ligands

In contrast, synthesis of 3,4-diphosphorylthiophenes requires more elaboration because of low reactivity of 3,4-positions of thiophene and unavailability of 3,4-dihalo or dimetallated thiophenes. Minami et al. synthesized 3,4-diphosphoryl thiophenes 16 as shown in Scheme 24 [46], Bis(phosphoryl)butadiene 17 was synthesized from 2-butyne-l,4-diol. Double addition of sodium sulfide to 17 gave tetrahydrothiophene 18. Oxidation of 18 to the corresponding sulfoxide 19 followed by dehydration gave dihydrothiophene 20. Final oxidation of 20 afforded 3,4-diphosphorylthiophene 16. 3,4-Diphosphorylthiophene derivative 21 was also synthesized by Pd catalyzed phosphorylation of 2,5-disubstituted-3,4-dihalothiophene and converted to diphosphine ligand for Rh catalysts for asymmetric hydrogenation (Scheme 25) [47],... 

Mixed-ligand anions [RC=CAuX] are rare in organogold chemistry. Selected examples have been obtained from reactions of [RC=CAuL oligomers with halides Q+X, from Q[Au(acac)2] salts with alkynes, followed by acids HX in the molar ratio 1 1 1, and from complexes (tht)AuCl (tht = tetrahydrothiophene) or [(Ph3P)2C]AuCl with an alkyne and a base (1 1 1). Known examples of products include salts Q+[HC=CAuCl/Br]-72 and [(Ph3P)2CH]+[PhC=CAuCl]. 52,53 Anions with mixed alkynyl/aryl substituents are present in... 

The synthesis of pure metalacycle la from [Ir(COD)Cl]2 and LI requires only amine base and heat, followed by precipitation and removal of amine hydrochloride. However, this complex was typically generated in situ during early studies by the treatment of a combination of [lr(COD)Cl]2 and LI with an amine base, such as uPrNH2, l,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), or l,8-diazabicyclo[5.4.0] undec-7-ene (DBU). If a 1 1 ratio of iridium to ligand is used, a mixture of la and [Ir(COD)Cl]2 is produced. Helmchen et al. have reported that catalyst activation in the presence of tetrahydrothiophene (THT) prevents coordination of the k -phosphoramidite [71]. 

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