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Chapter 4: Functionalization of diamondoid phosphines
83
Chapter 4: Functionalization of diamondoid phosphines
The synthesis of diamondoids having two different reactive functions is a requirement for their use as building blocks for the preparation of organohybrids based on the reactivity differences of the two functions. We thus found it rather surprising that to date no studies have been devoted to the unequal functionalization of adamantyl- and diamantylphosphines despite the high potential of such structures.
In our present case we anticipated that difunctionalized diamondoids, bearing both a phosphino group and another reactive function (hydroxy, halide) would be of general interest beyond the present objective of carbon-metal hybrid construction. The main problem we anticipated was the conservation of sufficient volatility for efficient ordering as self-assembly. However, regarding the good volatility demonstrated in Chapter 2 for hydroxylated diamantanes, it appears reasonable to think that, on this basis, some volatile functionalized diamondoid phosphines may be generated, for instance by tuning the substituents onto phosphorus.
4.1. Short review of the synthesis and applications of diamondoid phosphines
As discussed in Chapter 1, diamondoid phosphines were firstly accessible from adamantane or 1-bromo/hydroxyadamantane. The Schemes 4.1 and 4.2 complement the general results reviewed in Chapter 1 (shown here in grey) with further details on the state-of-the-art concerning diamondoid phosphine synthesis.
The 1-adamantylphosphonic dichloride 126 can be prepared from 1-bromoadamantane 2 with an excess of AlBr3 in PCl31,2 via a complex [(1-Ad)PCl3+AlBr4-] and also from 1-hydroxyadamantane 6 with PCl3
in warm concentrated sulfuric acid.3 The primary adamantylphosphine 129 is obtained in three steps from 126 through reaction with (p-CH3OC6H4PS2)2 (a.k.a. Lawesson’s reagent), sulfide reduction with PPh3
followed by reduction with LiAlH4.4 This synthetic pathway can be shortened to a single step by direct
1 H. Stetter, W. –D. Last. Chem. Ber., 1969, 102, 3364-3366. Über Adamantan-phosphonsäure-(1)-dichlorid.
2 1-Adamantylphosphonic dibromide from reflux 1-bromoadamantane with 21 eq. of PBr3 and 1.5 eq. of AlBr3 for 3 h, 24% yield:
H. Duddeck, M. H. A. Elgamal, A. G. Hanna. Phosphorus and Sulfur, 1986, 28, 307-314. Synthesis and Mass Spectra of Adamantylphosphoryl Derivatives.
3 I. K. Moiseev, N. V. Makarova, M. N. Zemtsova. Russian Chem. Rev., 1999, 68, 1001-1020. Reactions of adamantanes in electrophilic media.
4 M. Gouygou, G. Etemad-Moghadam, M. Koenig. Synthesis, 1987, 5, 508-509. A Convenient Method for the Synthesis of 1-Adamantyldichlorophosphine.
Chapter 4: Functionalization of diamondoid phosphines
84 reduction of 126 with LiAlH4 in THF under mild conditions to get 129. This route has been developed by Stetter1 and patented by Eastham.5
Reduction of 116 with HSiCl3 or with LiAlH4 gives the secondary phosphine 117.6,7 The di-1-adamantyl phosphinic chloride 116 can be prepared by refluxing adamantane 1 in 5 eq. of PCl3 with 1 eq. of AlCl3.5,7 The di-1-adamantylphosphine 117 treated with COCl2 and DBU leads to di-1-adamantylchlorophosphine 118 that is a valuable starting materials in organophosphorus chemistry.7,8 Alternatively, the compound 118 can also be achieved from refluxing the Grignard reagent 60 in diethyl ether with an excess of PCl3.9 The cousin organophosphorus compounds tert-butyl-1-adamantylchlorophosphine 159 and 1-adamantyl phenylphosphonic chloride 160 can also be synthesized from 60 by reaction with 1 equivalent of t-BuPCl2
and PhPCl2, respectively.10,11 The oxide of tert-butyl-1-adamantylchlorophosphine 161 is formed from reaction between 1-hydroxyadamantane 6 or 1-bromoadamantane 2 with PCl2Ph in sulfuric acid.12,13
The alkylphosphines 124 and 125 can be prepared from 60.14 Another route in order to get the tertiary phosphine 120 is using chlorinated secondary phosphine 118 with a Grignard reagent and CuBr.8 Brown et al. used 1-bromoadamantane 2 with silver triflate, HPPh2 and hydrogen peroxide to yield oxide phosphine 126.15
5 G. R. Eastham, P. A. Cameron, R. P. Tooze, K. J. Cavell, P. G. Edwards, D. L. Coleman. PCT Int. Appl. (2004), WO 2004014552 A1 20040219. Preparation of an aryl-bridged adamantylphosphine catalytic system for carbonylation of olefins.
6 HSiCl3: (a) H. Fritzsche, U. Hasserodt, F. Korte. Chem. Ber., 1965, 98, 1681-1687. Reduction of organic compounds of pentavalent phosphorus to phosphines. III. Preparation of primary and secondary phosphines with silanes. (b) J. R. Goerlich, R.
Schmutzler. Phosphorus, Sulfur, and Silicon, 1993, 81, 141-148. Di-1-adamantylphosphine, a highly sterically hindered phosphine. Preparation and reactions.
7J. R. Goerlich, R. Schmutzler. Phosphorus, Sulfur, and Silicon, 1995, 102, 211-215. Organophosphorus Compounds with Tertiary alkyl substituents. VI: A convenient Method for the Preparation of di-1-adamantylphosphine and di-1-adamantylchlorophosphine.
8 CCl4: A. Köllhofer, H. Plenio. Chem. Eur. J., 2003, 9, 1416-1425. Homogeneous Catalysts Supported on Soluble Polymers:
Biphasic Sonogashira Coupling of Aryl Halides and Acetylenes Using MeOPEG-Bound Phosphine-Palladium Catalysts for Efficient Catalyst Recycling.
9 S. L. Buchwald, D. W. Old, P. J. Wolfe, M. Palucki, K. Kamikawa. U. S. Patent (2001), US 6307087 B1 20011023. Ligands for metals and improved metal-catalyzed processes based thereon.
10 tBuPCl2: M. Su, S. L. Buchwald. Angew. Chem. Int. Ed., 2012, 51, 4710-4713. A Bulky Phosphine Ligand Allows for Palladium-Catalyzed amidation of Five-Membered Heterocycles as Electrophiles.
11 PhPCl2: S. Torker, A. Müller, R. Sigrist, P. Chen. Organometallics, 2010, 29, 2735-2751. Tuning the Steric Properties of a Metathesis Catalyst for Copolymerization of Norbornene and Cyclooctene toward Complete Alternation.
12 R. I. Yurchenko, L. P. Peresypkina. Zhurnal Obschchei Khimii, 1992, 62, 2389-2390. Acid dichlorides of phosphonous acids in synthesis of R-(1-adamantyl)chlorophosphinates.
13 R. I. Yurchenko, L. P. Peresypkina, V. V. Miroshnichenko, A. G. Yurchenko. Zhurnal Obshchei Khimii, 1993, 63, 1534-1539.
Phosphorylated adamantanes. XV. Phosphorylation of adamantane by trivalent phosphorus acid chloride in sulfuric acid.
14 J. P. Stambuli, S. R. Stauffer, K. H. Shaughnessy, J. F. Hartwig. J. Am. Chem. Soc., 2001, 123, 2677-2678. Screening of Homogeneous Catalysts by Fluorescence Resonance Energy Transfer. Identification of Catalysts for Room-Temperature Heck Reactions.
15 AgOTf: J. Prabagar, A. R. Cowley, J. M. Brown. Synlett, 2011, 16, 2351-2354. Electrophilic Routes to Tertiary Adamantyl and Diamantyl Phosphonium Salts.
Chapter 4: Functionalization of diamondoid phosphines
85 Scheme 4.1. Phosphorylated adamantane derivatives.
Chapter 4: Functionalization of diamondoid phosphines
86 The first phosphorylation of diamantane was reported by Olah et al. by mixing the diamantane 10 with PCl3 and AlCl3 to lead to 1-diamantylphosphonic dichloride.16 The Schreiner group found that the isomer 4-diamantylphosphonic dichloride 138 was obtained instead (Scheme 4.2). Di-diamantylphosphinic chloride 139 was also formed in this reaction. The synthesis of secondary and tertiary diamantyl and triamantyl phosphines was also reported.17 Reduction of 139 with HSiCl3 gave the corresponding phosphine 163 in 84% yield. The tertiary phosphine oxide 165 could be prepared via the phosphonium salt of di-diamantylphosphine 164 formed from phosphine 163.