The lactone of 1S,3S-1-hydroxy-1-diphenylphosphinomethyl-
2,2,3-tri-methyl-cyclopentan-3-carboxylic acid (4, CRC-PHOS) was
prepared from ( + )-camphanic acid methylester 1, and its complex
salt [Rh(CRC-PHOS)2NBD] · CI04 • THF (5) was isolated. The latter
exhibited rather a high rate, but low enantioselectivity in the first
attempt at asymmetric hydrogenation

A. Sega

G. Comisso

V. Šunjić

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CROATICA CHEMICA ACTA CCACAA 53 (3) 445-447 (1980) CCA-1223 YU ISSN 0011-1643 UDC 547.5 Preliminary Communication A Chiral Phosphine (CRC-PHOS) Derived from ( + )-Champhanic Acid. A New Ligand for Homogeneous Asymmetric Hydrogenation G. Comisso, A. Sega, and V. Sunjic CRC, Chemicai Research Company, 33048 San Giovanni al Natisone (UD) Italy Received April 7, 1980 The lactone of 1S,3S-1-hydroxy-1-diphenylphosphinomethyl--2,2,3-tri-methyl-cyclopentan-3-carboxylic acid (4, CRC-PHOS) was prepared from ( + )-camphanic acid methylester 1, and its complex salt [Rh(CRC-PHOS)2NBD] · CI04 • THF (5) was isolated. The latter exhibited rather a high rate, but low enantioselectivity in the first attempt at asymmetric hydrogenation. Recently, Bosnich rationalized1 the existing knowledge in the field of »tailoring« of chiral phosphine ligands in transition metal complexes as homo-geneous catalysts for asymmetric hydrogenation. Among specific features required of chiral monophosphines to achieve high enantioselectivity, the presence of an additional coordination site, usually an oxygen atom, is the most important2•3• The »lock and key« relation between catalytic complex and substrate still deserves general full attention in this field, however. Thus we have directed our attention to the preparation of a new chiral phosphine coded CRC-PHOS, and its catalytic activity and conformation in solution'. Camphanic acid methyl ester5 was reduced with complete site-selectivity to the alcohol 2 (88,90/o, m.p. 179-180 °c, [a]o + 1.85 ° (c = 1.90 in CHC13) the lactonic group remaining unaffected. Tosylaticm in pyridine afforded 3 (930/o, m.p. 116-117 °C, [a]o + 16,3 (c = 2.12 in CHC13)), which was reacted with diphenylphosphine lithium in THF at -10 °c to afford 4 (53,40/o, colourless oil after chromatography on silica with n-hexane/acetone (7 : 3) as eluant, [a]o-11.2° (c = 1.93 in CHC13).7 A catronic complex [Rh(CRC-PHOS)2NBD] · Cl04 (5, NBD-norbornadiene) was prepared by the reaction of 4 with [(NBD)2Rh] · Cl04 in THF for 1 h at room temperature. It precipitated from THF on slow addition of n-hexane as a fine orange-red powder which contained one mole of THF and exhibited amorphous structure, as ascertained b.Y X-ray diffraction8• cooc_~ Cf2-X -0 ~ {~~Z7~}-~0{"'2wrn~J~P'Q x ~o l 2 OH :J: OTs !!. (CRC-PHOS) 446 G. COMISSO ET AL. The two lactone groups in the complex 5 are presumed to coordinate via the tetrahedral oxygen, since low coordination ability was found for the carbonyl oxygen in esters9, thus assuring a certain degree of conformational rigidity to the catalytic species. Hydrogenations of the two model substrates 6 and 8 were routinely carried out in the presence of 5 and triethylamine10• The reactions proceeded to com-pletion at ambient temperature. The rate of hydrogenation of 6 corresponded .§ (Sl-1 NHCOCH3 o--AcooH NHCOC~ o-A~OOH !Sl-i · approx. to that obtained with (-)-DIOP, (2,3-isopropylidene-2,3-dihydroxy-1,4 bis(diphenylphosphino)butane) while 8 was reduced at somewhat lower rate than described11• Both products of hydrogenation, 7 and 9, possess S-configu-ration12. Low enantiomeric excess was achieved in the first series of experi-ments, the data of Table I listing the first results obtained on variation of some reaction parameters. Although these preliminary results may indicate low conformational rigidity of the phosphine ligand in 5, a search for the reaction conditions which could afford higher enantioselectivity in hydrogenation of some other substrates is in progress. TABLE I Asymmetric Hydrogenation of 6 and 8 with [Rh(CRC-PHOS)2NBD] · Cl04" (I) ..., cu Substrate/5 Press. Temp. Time e.e. (0/e)• '""' Solvent ..., - --tll ratio (config.) .c atm oC h ::s en 6 EtOH abs. 86 95.5 20 23 13.6 (S) 6 EtOH abs./Bz(l :2) 86 70.0 20 20 14.9 (S) 6 EtOH abs. 86 84.0 20 55 3.1 (S) 6 EtOH abs. 86 14.0 50 3 12.6 (S) 6 EtOH abs. 86 70.0 2 21° 14.1 (S) 6 EtOH abs. 86° 14.0 50 3 13.2 (S) 8 EtOH 99.80/o 70 84.0 20 65 3.2 (S) 8 EtOH 99.80/o 70 84.0 20 48 3.4 (S) • All hydrogenations were carried out with EtaN added in the ratio 7.7/1 (mmol/mmole) related to S. h Enantiomeric excess (e. e.) was calculated on the basis of the reported values for the optical pure compounds : S-7; [«lo - 57.4 (N. Blazevic, M. Zinic, T. Kova~. v. Sunjic and F. Kajfez, Acta Pharm. Jugostav. 25 (1975) 155) ; S-9 ; [«Jn + 46.0 (ref. 1) • Chemical conversion was ca. 80'/•. In all other runs conversion was quant itative according to TLC, Isolated yields were over 90°/o. • The total cone. of 6 was 1.12 lo-• M, in other runs it was 1.12 io-1 M. CHIRAL PHOSPHINE 447 REFERENCES AND NOTES 1. M. D. Fry z u k and B. Bos n i ch, J . Amer. Chem. Soc. 99 (1977) 6262. 2. W. S. Knowles, M. J. Sabacky, and B. D. Vineyard, Chem. Commun. 1972, 10. 3. W. S. Knowles, M. J. Saba ck y, B. D. Vineyard, and D. J . Wein-k au ff, J. Amer. Chem. Soc. 97 (1975) 2567. 4. LIS-NMR measurements and computer assisted data evaluation were performed for CRC-PHOS and some related model compounds in order to determine con-formation of the lanthanide complexes in solution - manuscript in preparation. 5. Prepared from ( + )-camphanic acid, lit.6 mp. 108-109 °c. [o.]n-22.8 °c. (c == 3.25 in CHC13) . ( + )-Camphanic acid (now available commercially from Fluka) is a well established chiral resolving agent, see e.g. H. Gerl a ch and W. M i.i 11 er, Helv. Chim. Acta 55 (1972) 2277; V. Sun j i c, F. Ka j fez, D. Ko 1 bah, and N. Blazevic, Croat. Chem. Acta 43 (1971) 205; A. Kon oval, Y. Yurczak, and A. Zam o j ski, Tetrahedron 32 (1976) 2957. 6. V. Sun j i c, F . Ka j fez, M. O kl ob di j a, and M. Strom a r, Croat. Chem. Acta 45 (1973) 569. 7. Satisfactory spectral and microanalytical data were obtained for all new com-pounds. 8. B. Prod i c - Ko j i c (»Ruder Boskovic« Institute, Zagreb) - private commu-nication. 9. P. Br au stein, D. Matt, F . Mathey, and D. Th av a rd, J. Chem. Research 1978, 232; 3041. 10. It is interesting to note that complex 5 exhibited high diastereoselectivity in hydrogenation of metacycline-hydrochloride into 6-o.-methyl-6-deoxy-tetracycline. At 14 atm and 100 °c the 6-epimer was quantitatively formed after 4 h., diaste-romeric purity being over 950/o. 11. H. B. Kagan and T. P. Dang, J. Amer. Chem. Soc. 94 (1972) 6429. 12. The S-configuration has been recently determined by chemical and spectroscopic correlation, for ( + )-a-(3-benzoyl)-phenyl propionic acid, which was obtained in 660/o e. e. by asymmetric hydrogenation of 6 with (- )-DIOP.13 13. G. Com is so, M. Mihal i c, F . Ka j fez, V. Sun j i c, and G. Sn at z k e, Gazz. Chim. Ital. 110 (1980) 123. SAZETAK Kiralni fosfin (CRC-PBOS) izveden od ( + )-kamfan-kiseline. Novi ligand za bomogenu asimetricnu bidrogenaciju G. Comisso, A. Sega i V. Sunjic Lakton 1S,3S-1-hidroksi-1-difenilfosfometil-2,2,3-trimetil-ciklopen tan-3-karbo-ksilne kiseline (4, CRC-PHOS), pripravljen je posavsi od metilnog estera ( + )-kam-fan-kiseline, i izolirana je njegova kompleksna sol [Rh(CRC-PHOS)2NBD] · Cl04 • · THF (5). Taj je kataliticki kompleks pokazao visoku reaktivnost, ali nisku enantio-selektivnost u prvim poku5ajima asimetrienih hidrogenacija. CRC, CHEMICAL RESEARCH COMPANY. 33048 SAN GIOVANNI AL NATISONE (UD) IT ALI.TA Prispjelo 7. travnja 1980. 

A Chiral Phosphine (CRC-PHOS) Derived from ( + )-Champhanic Acid. A New Ligand for Homogeneous Asymmetric Hydrogenation

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