Oxygen-Containing 10-, 15-, and 20-Membered Macrocyclic Cobalt Complexes from Co₂(CO)₆-Bispropargylic Alcohol 

David Díaz Díaz ^1,*,† Juan Pedro Ceñal ² and Víctor S. Martín ^1,*

Received: 6 November 2007; in revised form: 22 January 2008 / Accepted: 23 January 2008 / Published: 25 March 2008

Abstract: Novel 10-, 15-, and 20-membered oxygen-containing macrocyclic cobalt complexes (3, 4, and 5 respectively) were obtained in moderate combined yield via double nucleophilic substitution of the hexacarbonyldicobalt-coordinated monoyne diol [{Co₂(CO)₆(μ-η²-HOCH₂C≡CCH₂OH)}] (1) upon BF₃·OEt₂ treatment in the presence of (Z)-2-butene-1,4-diol (2) at room temperature. The products distribution was found to be highly concentration dependent.

 Keywords: Nicholas reaction, cobalt, alkyne complexes, macrocycles

The Nicholas reaction is a powerful and versatile synthetic tool in organic synthesis. It basically consists in the nucleophilic attack on a Co₂(CO)₆-propargylic cation, which is generated by adding either protic acids or Lewis acids, mainly trifluoromethane sulfonic acid, HBF₄·OEt₂ and BF₃·OEt₂ on Co₂(CO)₆-propargylic alcohols. The reaction works well with a variety of nucleophiles to form new bonds between the propargylic carbon and atoms that include carbon, oxygen, hydrogen and nitrogen. The procedure can be applied inter- or intra-molecularly in solution or in solid phase [1].

 Experimental Section 

 General 

 ¹H and ¹³C NMR spectra were recorded at 25 °C on Bruker Avance-300 spectrometer in CDCl₃ as solvent, and chemical shifts are reported relative to Me₄Si. Low- and high-resolution mass spectra were obtained by using a Micromass Autospec spectrometer. Elemental analysis was performed on a Fisons Instrument EA 1108 CHNS-O analyzer. Infrared spectra were recorded on a Bruker IFS 55 spectrophotometer on compounds dispersed on a CaF₂ disc (20 × 2 mm). Column chromatographies were performed on Merck silica gel, 60 Å and 0.2-0.5 mm. Methylene chloride was dried by distillation over calcium hydride prior to use. All reagents were commercially available and used without further purification. Hexacarbonyldicobalt-coordinated monoyne diol [{Co₂(CO)₆(μ-η²-HOCH₂C≡CCH₂OH)}] (1) was prepared as reported in the literature [2].

Synthesis of cobalt-complexed oxygen-containing macrocyclics 3-5:

To a stirred solution of [{Co₂(CO)₆(μ-η²-HOCH₂C≡CCH₂OH)}] (1) (200 mg, 0.54 mmol) in CH₂Cl₂ (54 mL, 0.01M) were consecutively added (Z)-2-butene-1,4-diol (2)  (45 mL, 0.54 mmol) and BF₃·OEt₂ (137 ml, 1.08 mmol) under an argon atmosphere at room temperature. The reaction mixture was monitored by TLC. The mixture was poured with vigorous stirring into a saturated solution of NaHCO₃ at 0 °C for 15 min and extracted with CH₂Cl₂. The combined organic phases were washed with brine, dried (MgSO₄), concentrated, and the products separated by silica gel column chromatography. Macrocycles 3, 4, and 5 were isolated as red oils in a ratio 1:10:4 respectively and 62% combined yield. Interestingly, under more concentrated conditions (0.02M) the ratio of the macrocycles was found to be 1:3:8 respectively. It is worth to mention that traces of other cobalt complexes were also formed along with the isolated macrocycles, although these minor products could not be isolated and characterized in the preliminary studies.

8,13-Bis-(hexacarbonyldicobalt)-μ₂-{η²-1,6,11-trioxa-cyclopentadec-3-ene-8,13-diyne} (3):

¹H NMR (300 MHz, CDCl₃) d = 4.28 (m, 4H), 4.71 (s, 4H), 4.95 (s, 4H), 5.76 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) d = 66.6 (t), 71.0 (t), 130.6 (d), 199.2 (s); IR (thin film) υ (cm^-1) 2093, 2053, 2022; FAB-MS m/z (relative intensity) 779 (M+1)⁺ (8) , 778 (M)⁺ (30), 722 (M−2CO)⁺ (12), 694 (M−3CO)⁺ (10), 638 (M−5CO)⁺ (13), 610 (M−6CO)⁺ (17), 553 (100). HMRS calcd for C₂₄H₁₄Co₄O₁₅ (M-1)⁺ 777.76606, found 777.76680. 

3-Hexacarbonyldicobalt-μ₂-{η²-3,4-didehydro-2,5,7,10-tetrahydro-1,6-dioxecino} (4):

¹H NMR (300 MHz, CDCl₃) d = 4.23 (m, 4H), 4.71 (s, 4H), 5.76 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) d = 66.5 (t), 70.6 (t), 129.3 (d), 194.3 (s); IR (thin film) υ (cm^-1) 2094, 2054, 2022; FAB-MS m/z (relative intensity) 425 (M+1)⁺ (22) , 424 (M−1)⁺ (18), 396 (M−CO)⁺ (22), 368 (M−2CO)⁺ (38), 365 (100), 340 (M−3CO)⁺ (16), 312 (M−4CO)⁺ (29). HMRS calcd for C₁₄H₉Co₂O₈ (M-1)⁺ 422.89614, found 444.89578.

8,18-Bis-(hexacarbonyldicobalt)-μ₂-{η²-1,6,11,16-tetraoxa-cycloicosa-3,13-diene-8,18-diyne} (5):

¹H NMR (300 MHz, CDCl₃) d = 4.45 (m, 8H), 4.88 (s, 8H), 5.86 (m, 4H); ¹³C NMR (75 MHz, CDCl₃) d = 66.6 (t), 71.0 (t), 130.6 (d); IR (thin film) υ (cm^-1) 2060, 2032, 2012; FAB-MS m/z (relative intensity) 849 (M+1)⁺ (26) , 848 (M)⁺ (21), 820 (M−CO)⁺ (20), 764 (M−3CO)⁺ (33), 736 (M−4CO)⁺ (30), 708 (M−5CO)⁺ (29), 680 (M−6CO)⁺ (21), 652 (M−7CO)⁺ (21), 624 (M−8CO)⁺ (26), 602 (100), 596 (M−9CO)⁺ (20). Anal. Calcd for C₂₈H₂₀Co₄O₁₆: C, 39.65; H, 2.38. Found: C, 39.86; H, 2.51.

Acknowledgements

This research was financially supported by the Ministerio de Educación y Ciencia of Spain, co-financed by the European Regional Development Fund (CTQ2005-09074-C02-01/BQU) and the Canary Islands Government.

References and Notes

1. For reviews on the chemistry uses of cobalt-complexed propargylic cations and related issues, see: (a) Nicholas, K. M. Acc. Chem. Res. 1987, 20, 207-221; (b) Caffyn, A. J. M.; Nicholas, K. M. In Comprehensive Organometallic Chemistry II; Hegedus, L. S., Ed.; Pergamon: Oxford, 1995; Vol. 12, Chapter 7.1, pp 685-702; (c) Welker, M. E. Current Organic Chemistry 2001, 5, 785-807; (d) Green, J. R. Current Organic Chemistry 2001, 5, 809-826; (e) Müller, T. J. J. Eur. J. Org. Chem. 2001, 2021-2033; (f) Teobald, B. J. Tetrahedron 2002, 58, 4133-4170; (g) Fryatt, R.; Christie S. D. R. J. Chem. Soc., Perkin Trans. 1 2002, 447-4
2. For other uses of 1 as masked dielectrophiles in cyclization reactions, see: (a) Gruselle, M.; Malézieux, B.; Vaissermann, J.; Amouri, H. Organometallics 1998, 17, 2337-2343; (b) Lu, Y.; Green, J. R. Synlett 2001, 243-247; (c) Soleilhavoup, M.; Saccavini, C.; Lepetit, C.; Lavigne, G.; Maurette, L.; Donnadieu, B.; Chauvin, R. Organometallics 2002, 21, 871-883.
3.  For a complete study on the synthesis of oxygen-containing macrocycles from the analog 1,3-diyne diol [{Co₂(CO)₆(μ-η²-HOCH₂C₂-)}₂], see: Hope-Weeks, L. J.; Mays, M. J.; Solan, G. A. Eur. J. Inorg. Chem. 2007, 3101-3114. 
4. For the synthesis of sulfur-containing macrocycles from 1, see: (a) Gelling, A.; Jeffery, J. C.; Povey, D. C.; Went, M. J. J. Chem. Soc., Chem. Commun. 1991, 349-351; (b) Dernirhan, F.; Irişli, S.; Salek, S. N.; Şentük, O. S.; Went, M. J.; Jeferry, J. C. J. Organomet. Chem. 1993, 453, C30-C31; (c) Dernirhan, F.; Gelling, A.; Irişli, S.; Jeferry, J. C.; Salek, S. N.; Şentük, O. S.; Went, M. J. J. Chem. Soc. Dalton Trans. 1993, 2765-2773; (d) Bennett, S. C.; Jeffery, J. C.; Went, M. J. J. Chem. Soc. Dalton Trans. 1994, 3171-3176; (e) Davies, J. E.; Hope-Weeks, L. J., Mays, M. S.; Raithby, P. R. Chem. Commun. 2000, 1411-1412.