Transition metal catalyzed oxidations, 3. Reaction of 4‐hydroxy[2.2]paracyclophane with the mimoun molybdenum oxodiperoxo complex [Mo(O₂)₂O]· Py · HMPT

Abstract

Treatment of I-hydroxy[2.2]paracyclophane (1) with the Mim-(4). This dienone dimerizes at room temperature to afford the oun molybdenum oxodiperoxo complex [Mo(O&O] . Py . Diels-Alder adduct 5, whose structure was confirmed by X-ray HMPT gives 3,4-dihydro-3-hydroxy-4-oxo[2.2]paracyclophane analysis. Recently, we have described the specific oxidation of phenols to ortho-quinones using tert-butyl hydroperoxide and transition metal complexes or the Mimoun molybdenum oxodiperoxo complex [Mo(O2),0]. Py . HMPT']. This reaction is initiated by replacement of one ligand of the complex by the phenol, as depicted in I, followed by oxygenation and dehydrogenation processes ' I. The exact mechanism of the oxygen transfer is as yet unknown. In this paper the reaction of 4-hydroxy[2.2]paracyclophane (1) with [MO(O')~-01. Pya HMPT is described; it provides insight into the nature of the oxygen-transfer step and yields a structurally new type of paracyclophane dimer.Miyahara et aL4) have described the isolation of a 1 : 1 mixture of the ortho-, 2, and the para-quinone 3 obtained by the reaction of 1 with diphenylselenic anhydride (Barton's reagentIn an attempt to improve the yield of 2, which is needed for further transformations, 1 was treated with the Mimoun molybdenum complex. However, only small amounts ( < 1 YO) of the deep red ortho-quinone 2 are formed with two equivalents of [Mo(O2),0]. Py . HMPT at 0°C in CH2C12, the major part of the product mixture consisting of two polar colorless compounds. The ratio of the new products depends strongly on the reaction conditions and the workup procedure. It soon became clear from the mass spectra that the less polar product is monomeric and an intermediate in the formation of the stable, dimeric oxidation product. Traces of acid or Lewis acid catalyze the dimerization.For instance, the NMR measurements in CDC13 have to be carried out immediately after termination of the oxidation since the monomer decomposes under these conditions (ca. 40% after 14 h). The monomer is more stable if the workup is carried out under neutral rather than acidic conditions, the molybdenum catalyst being removed by rapid filtration through a column of silica gel. In this case the monomer can be isolated in 75% yield. On the basis of spectral data (see experimental section) this compound is assigned the structure 4. Hydroxyketones of this type have previously been discussed as reaction intermediates in the epoxidation of various phanes6s7), but they have never been isolated. Interestingly, related hydroxylation products have been identified recently by Effenberger et a1." in the autoxidation of phloroglucinophanes. The structural assignment of 4 is supported by the structure of the dimer as determined by Xray analysis. As shown in Figure 1 this second compound has structure 5, i.e. it is formally a Diels-Alder dimer of 4. For the formation of 5, whose very complex NMR spectral data (experimental section) clearly show its highly asymmetric nature, it must be assumed that the terminal double r

Resolution and Novel Reactions of 4-Hydroxy[2.2]paracyclophane

“…25] NMR: Bruker AMX 400 (400 and 100 MHz, for 1 H and 13 C, respectively). For 1 H NMR spectroscopy the residual proton…”

The Synthesis of Pseudo‐Geminal, Pseudo‐Ortho and Ortho Hydroxy‐oxazolinyl[2.2]paracyclophanes for Use as Ligands in Asymmetric Catalysis

“…This technique is based on the optimum synthesis of 4-hydroxyA C H T U N G T R E N N U N G [2.2]paracyclophane described by Hopf and Krohn. [22] With our compounds, an improvement in yield was obtained by carrying out the reaction in a solvent mixture of Et 2 O:THF (3:1) instead of pure Et 2 O. The effect was largely due to the low solubility of the starting compounds in Et 2 O, in particular diastereoisomer 5b, the yield from which improved from 14 to 71 %.…”

Stereoselective Lateral Functionalization of Monosubstituted [2.2]Paracyclophanes by Directedortho-Metalation−Homologous Anionic Fries Rearrangement

“…The phrase ''workup in the usual manner'' refers to extraction of the reaction mixture with dichloromethane, drying of the combined organic extracts with Na 2 SO 4 or MgSO 4 , and evaporation of the solvent under reduced pressure. Ϫ 4-Hydroxy-[2.2]paracyclophane (1) [15] and 4-[2.2]paracyclophanecarbonyl chloride (8) [19] were synthesized according to literature procedures. (1) (1.5 g, 6.7 mmol) was added at 0°C to a suspension of NaH (300 mg, 12.5 mmol) in THF (60 mL).…”

“…[13] We chose the ortho-protected O- (4-[2.2]paracyclophanyl) diisopropylcarbamates 3a and 3b for studies of this homologous anionic Fries rearrangement, since the trialkylsilyl groups are easily removable by fluoride sources. [10,14] Compounds 3a and 3b were readily prepared from 4-hydroxy- [2.2]paracyclophane [15] (1) by carbamoylation to 2 followed by standard directed ortho-metalation (DoM) [14] and silylation with TMSCl and TESCl, respectively (Scheme 1). The application of the DoM strategy to O-( [2.2]paracycloScheme 1.…”