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Francesc X Roca

Publications and source records attributed to Francesc X Roca.

5 recordsLinked to original sources
PubMed2007

Second generation catalytic asymmetric synthesis of Tamiflu: allylic substitution route.

Catalytic asymmetric synthesis of Tamiflu, an important antiinfluenza drug, was achieved. After the catalytic enantioselective desymmetrization of meso-aziridine 3 with TMSN3, using a Y catalyst (1 mol %) derived from ligand 2, an allylic oxygen function and C1 unit on the C=C double bond were introduced through cyanophosphorylation of enone and allylic substitution with an oxygen nucleophile. This second generation route of Tamiflu is more practical than our previously reported route. [reaction: see text].

Catalysis↗
PubMed2005

SPANphos: trans-spanning diphosphines as cis chelating ligands!

Several SPANphos ligands based on a spirobichroman backbone, introduced as a putative trans ligand, form compounds of the type [Rh(nbd)(SPANphos)]BF(4) () in which both norbornadiene and SPANphos act as cis chelating ligands. The cyclooctadiene rhodium chloride derivatives form bimetallic complexes. Crystal structures for several of these compounds and free ligands are reported. Semiemperical AM1 and DFT calculations show that spirobichroman can assume several conformations, some of which are suitable for the formation of cis chelating SPANphos. All calculations on SPANphos complexes of PdCl(2), PtCl(2) and Rh(CO)Cl show that the trans complex is more stable by 4-10 kcal mol(-1). The cis conformation is enforced by the cis chelating norbornadiene ligand.

Journal Article↗
PubMed2005

Synthesis of planar chiral phosphapalladacycles by highly enantioselective transcyclopalladation.

The first highly enantioselective synthesis of planar chiral ferrocene phosphapalladacycles was performed by high-yielding asymmetric transcyclopalladation with cobalt oxazoline palladacycles (COP). Use of di-mu-acetatobis[(eta5-(S)-(pR)-2-(2'-(4'-isopropyl)oxazolinyl)cyclopentadienyl-C1,N3')(eta4-tetraphenylcyclobutadiene)cobalt]dipalladium(II), followed by acetate/chloride ligand exchange, gave (pS)-di-mu-chloro[2-(2-dicyclohexylphosphino)phenylferroene-C1,P)dipalladium(II) (95% ee). Similarly, diastereomeric di-mu-acetatobis[(eta5-(S)-(pS)-2-(2'-(4'-tert-butyl)oxazolinyl)cyclopentadienyl-C1,N3')(eta4-tetraphenylcyclobutadiene)cobalt]dipalladium(II) led to the enantiomeric (pR)-phosphapalladacycle (95% ee), revealing the control of these reactions by the element of planar chirality in COP. The reactions were extended to the synthesis of (pS)- and (pR)-di-mu-chloro[2-(2-diphenylphosphino)phenylferroene-C1,P)dipalladium(II) (78 and 92% ee, respectively). In all cases, the palladium-free precursors to COP were recovered for recycling.

Journal Article↗
PubMed2003

Synthesis of monodentate ferrocenylphosphines and their application to the palladium-catalyzed Suzuki reaction of aryl chlorides.

Racemic and enantiopure ((p)()S)-1-bromo-2-methylferrocene 6 were synthesized in 4 steps from 2-(4,4-dimethyloxazolinyl)ferrocene and (S)-2-(4-methylethyloxazolinyl)ferrocene, respectively (46 and 81% overall yield). Bromolithium exchange and addition of ClPR(2) gave the corresponding racemic or enantiopure 2-methylferrocenyl phosphine ligands 2-MeFcPR(2) 11 (R = Ph), 12 (R = Cy), and 13 (R = (t)Bu) in 28-93% yield. Use of PCl(3) gave the C(3)-symmetric phosphine (2-MeFc)(3)P 5 from ((p)()S)-6(72% yield) but racemic 6 did not lead to the formation of triferrocenyl phosphines. Combination of 5 and Pd(2)(dba)(3) gave an active catalyst for the Suzuki reaction of aryl chlorides, for example, 4-chlorotoluene and phenylboronic acid reacted at only 60 degrees C in dioxane (86% yield). Other examples are reported together with the use of 12 in this same protocol. From the X-ray crystal structure of 5 the cone angle was determined as 211 degrees. With this, and the electronic character of 11, 12, and other phosphines (derived from nu(CO) of trans-[(R(3)P)(2)Rh(CO)Cl]), an analysis is made of the steric and electronic influences on ligand activity in the Suzuki reaction.

Journal Article↗