Di-µ-Hydroxy-bis(N,N,N′,N′-tetramethylenediamine)copper(II) Chloride {[Cu(OH)˙TMEDA]₂Cl₂} Catalyzed Tandem Phosphorous-Carbon Bond Formation-Oxyfunctionalization: Efficient Synthesis of Phenacyl Tertiary
Phosphine-Boranes

Abstract

A novel [Cu(OH)˙TMEDA]₂Cl₂ catalyzed tandem reaction has been developed for the synthesis of a series of sterically and electronically divergent phenacyl tertiary phosphine-boranes.

Key words

phosphine-boranes - terminal alkynes - phenacyl tertiary phosphine-borane - copper iodide - methyl propiolate

Reference and Notes

• 1a Alonson F. Beletskaya M. Yus IP. Chem. Rev.  2004,  104:  3079 
• 1b Beller M. Seayad J. Tillack A. Jiao H. Angew. Chem. Int. Ed.  2004,  43:  3368 
• 1c Trost BM. Angew. Chem., Int. Ed. Engl.  1995,  34:  259 
• 1d Tani K. Kataoka Y. In Catalytic Heterofunctionalization   Togni A. Grutzmacher H. Wiley-VCH; Weinheim: 2001.  p.171 
• 1e Beletskaya I. Pelter A. Tetrahedron  1997,  53:  4957 
• 1f Comprehensive Handbook on Hydrosilylation   Marciniec B. Pergamon Press; Oxford: 1992. 
• 1g Pereyre M. Quintard JP. Rahm A. Tin in Organic Synthesis   Butterworth; London: 1987. 
• 2a Noyori R. Asymmetric Catalysis in Organic Synthesis   Wiley and Sons; New York: 1994.  Chap. 2.
• 2b Pietrusiewicz KM. Zablocka M. Chem. Rev.  1994,  94:  1375 
• 2c Yamanoi Y. Imamoto T. Rev. Heteroat. Chem.  1999,  20:  227 
• 2d Komarov IV. Borner A. Angew. Chem Int. Ed.  2001,  40:  1197 
• 2e Van Leeuwen PWNM. Kamer PCJ. Reek JNH. Dierkes P. Chem. Rev.  2000,  100:  2741 
• 3a Han LB. Hua R. Tanaka M. Angew. Chem. Int. Ed.  1998,  37:  94 
• 3b Allen A. Ma L. Lin W. Tetrahedron Lett.  2000,  41:  152 
• 3c Allen A. Ma L. Lin W. Tetrahedron Lett.  2002,  43:  3707 
• 3d Mirzaei F. Han LB. Tanaka M. Tetrahedron Lett.  2001,  42:  297 
• 3e Han LB. Mirzaei F. Zhao CQ. Tanaka M. J. Am Chem. Soc.  2000,  122:  5407 
• 3f Zhao CQ. Han LB. Tanaka M. Organometallics  2000,  19:  4196 
• 4 Reichwein JF. Patel MC. Pagenkopf BL. Org. Lett.  2000,  3:  4303 
• 5a Douglass MR. Marks TJ. J. Am. Chem. Soc.  2000,  122:  1824 
• 5b Douglass MR. Stern CL. Marks TJ.
  J. Am. Chem. Soc.  2001,  123:  10221 
• 5c Douglass MR. Ogasawara M. Hong S. Metz MV. Marks TJ. Organometallics  2002,  21:  283 
• 6a Mimeau D. Gaumont AC. J. Org. Chem.  2003,  68:  7016 
• 6b Bourumeau K. Gaumont AC. Denis JM. Tetrahedron Lett.  1997,  38:  1923 
• 6c Bourumeau K. Gaumont AC. Denis JM. J Organomet. Chem.  1997,  529:  205 
• 7 Kumaraswamy G. Venkata Rao G. RamaKrishna G. Synlett  2006,  1122 
• 14a Hamada T. Ye X. Stahl SS. J. Am. Chem. Soc.  2008,  130:  833 
• 14b Kumaraswamy G. Pitchaiah G. Ram Krishna G. RamaKrishna DS. Sadaiah K. Tetrahedron Lett.  2006,  47:  2013 

8

Other copper salts evaluated for this transformation are CuOTf, CuOAc, CuCl, CuCl₂, Cu(Piv)₂, [Cu(MeCN)₄]PF₆, and Cu(acac)₂. Except CuCl₂ (30%), none gave target compound.

9

Various solvents and bases were screened for the optimization of yield of 3b. Halogenated solvents (CH₂Cl₂, CHCl₃, DCE) and toluene failed to give the product. In addition to MeCN, only the aprotic solvent DMF was successful albeit in low yield (40%). Bases such as K₂CO₃, Na₂CO₃, NaHCO₃, K₃PO₄, and KOt-Bu did not yield the observed product.

10

We have performed the reaction under aerobic conditions and under inert atmosphere. In both cases the product formation was observed but in open air a slightly better yield was obtained. Further, using an oxygen balloon, the reaction did not proceed. These experiments imply that the dissolved air is essential for the product formation. At present, we have no satisfactory explanation for this phenomenon and it clearly needs further work.

11

Typical Procedure
Secondary phosphine-borane (±)-1b (198 mg, 1.1 mmol) and phenyl acetylene (2a, 198 mg, 1.0 mmol) were dissolved in MeCN (5 mL). To this reaction mixture, [Cu(OH)˙TMEDA]₂Cl₂ (38 mg, 10 mol%) and Et₃N (20 mg, 20 mol%) were added sequentially. The resulting reaction mixture was stirred 6 h at ambient temperature. The reaction mixture was quenched with sat. NH₄Cl solution and extracted with EtOAc (2 × 10 mL) and washed with brine solution. The combined extracts were dried over anhyd Na₂SO₄ and filtered, and evaporation under reduced pressure resulted in a crude residue. The residue was subjected to SiO₂ column chromatography, and it furnished the phenacyl tertiary phosphine-borane 3b in 80% yield (262 mg).
^¹H NMR (300 MHz, CDCl₃): δ = 1.18 (d, J = 14.3 Hz, 9 H), 3.55-3.85 (m, 2 H), 7.36-7.53 (m, 6 H), 7.76-7.89 (m, 4 H).^¹³C NMR (75 MHz, CDCl₃): δ = 25.4, 29.8, 30.1, 128.1, 128.2, 129.0, 131.3, 131.4, 133.4, 133.5, 133.6, 195.9. IR (KBr): 2925, 2855, 2386, 1668, 1143, 1068, 996, 738 cm^-¹. MS-FAB: m/z = 297 [M - 1]⁺. HRMS (ESI-MS): m/z calcd for C₁₈H₂₄PBONa: 321.1415; found: 321.1415.

12

The crystal belongs to the monoclinic crystal system, space group is Cc with a = 11.6520 (7) Å, b = 22.6559 (14) Å, c = 7.5701 (5) Å, β = 117.933 (1), V = 1765.58 (19) Å^³, ρ _calc = 1.122 mg m^-³, λ = 0.71073Å, µ(Mo Kα) = 0.152
mm^-¹, F ₀₀₀ = 640, T = 294 (2) K. Data collection yielded 8337 reflection resulting in 3095 unique, averaged reflection, 3041 with I > 2σ(I), θ range: 1.80-25.00˚. Full-matrix least-squares refinement led to a final R = 0.0293, wR = 0.0770 and GOF = 1.013. Intensity data were measured on Bruker Smart Apex with CCD area detector. CCDC 714891 contains the supplementary crystallographic data for the structure 3b. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

13

Transformation of styrene 2i into a phenacyl tertiary phosphine-borane 3b can be tentatively rationalized on the basis of Wacker-type oxidation.