A study of deuterium exchange in adamantane carboxylic acids and alcohols under electron impact

The mass spectra of 1-adamantyl substituted carboxylic acids and alcohols with and without deuterated hydroxyl groups were studied. Deuterium exchange between functional group and adamantane nucleus was observed and a possible explantation of the phenomenon is given.     

Novel 2,4-methanoadamantane-benzazepine by domino photochemistry of N-(1-adamantyl)phthalimide

The photochemical reaction of N-(1-adamantyl)phthalimide (1) gives cleanly one product, the novel hexacyclic benzazepine derivative of 2,4-methanoadamantane 2. Its structure was characterized by spectroscopic methods and X-ray analysis and represent the first example of the 2-azahexacyclo[8.7.1.1 (1,4).0 (4,9).0 (11,16).0 (12,18)]nonadeca-4,6,8-triene skeleton. The product is formed by a domino process of two consecutive excited-state intramolecular gamma-hydrogen-transfer reactions. Base hydrolysis of the benzazepine 2 gives in high yield the keto derivative of the 1,2-substituted adamantane epsilon-amino acid 3.     

A short-cut from 1-acetyl adamantane to 2-(1-adamantyl)pyrroles

The oxime of 1-acetyl adamantane 2 is added to acetylene (KOH/DMSO, 70 °C, initial acetylene pressure 13 atm, 30 min) to afford the corresponding O-vinyl oxime 5 in 80% yield. The latter upon heating (DMSO, 120 °C, 1 h) gives 2-(1-adamantyl)pyrrole 3, 1-acetyl adamantane 1, and adamantane (6:3:1 mass ratio), the yield of the pyrrole 3 being 83% (based on 1-acetyl adamantane 1 consumed). Under harsher conditions (NaOH/DMSO, 130 °C, atmospheric pressure of acetylene, 4 h) oxime 2 reacts with acetylene to furnish pyrrole 3, 1-acetyl adamantane 1, 1-vinyl adamantane 9, and adamantane (6:7:3:1 mass ratio), with the isolated yield of pyrrole 3 reaching 34%. Under pressure (NaOH/DMSO, 120 °C, initial acetylene pressure 14 atm, 1 h) the same reaction leads to 2-(1-adamantyl)-1-vinylpyrrole 4 and ketone 1 in 48% (based on consumed ketone 1) and 24% yields, respectively. The pyrrole 4 is easily deprotected to the corresponding 1H-pyrrole 3 in 77% yield by treatment (aqueous MeCN) with Hg(OAc)₂ and NaBH₄.     

Synthesis of functionalized 5-(3-R-1-adamantyl)uracils and related compounds

Efficient synthetic approaches to functionalized 5-(3-R-1-adamantyl)uracils and related compounds (R=OH, COOH, NH₂, etc.) are described. The selective hydroxylation of the adamantane tertiary C-H bonds in 5-(1-adamantyl)uracils with H₂SO₄ in trifluoroacetic anhydride is used as the key step. Subsequent electrophilic reactions of 5-(3-hydroxy-1-adamantyl)uracils with N- and C-nucleophiles in CF₃COOH, H₂SO₄ or H₂SO₄/AcOH media yielded derivatives with amide, amino, aryl, carboxy and thiourea groups in the adamantane core. The preliminary evaluation of the antiviral activity revealed that some of the synthesized species display moderate antiviral activity against HSV-1 (SI∼20) in Vero cells.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-[4-hydroxy(alkoxy,acyloxy)-3-alkoxy-benzylidene]-1-(1-adamantyl)ethanamines from 1-(1-adamantyl)ethanamine hydrochloride (Rimantadine)

Reactions of 1-(1-adamantyl)ethanamine with vanillin, vanillal, veratraldehyde, 3-ethoxy-4-methoxybenzaldehyde, and 4-formyl-2-methoxy(ethoxy)phenyl esters gave previously unknown Schiff bases containing an adamantane fragment.     

Oxidative aromatization of olefins with dioxygen catalyzed by palladium trifluoroacetate

Molecular oxygen can replace sacrificial olefins as the hydrogen acceptor in the palladium trifluoroacetate catalyzed dehydrogenation of cyclohexene and related cyclic olefins into aromatics. One of the major drawbacks of the homogeneous system is the tendency of the palladium trifluoroacetate to precipitate as palladium(0) at elevated temperatures. The use of better ligands affords catalysts that can operate at higher temperatures, although they are less reactive than palladium trifluoroacetate.     

Synthesis of pyrazoles and pyrazolones from 1,3- and 1,4-diketones of the adamantane series

Various pyrazole and dihydropyrazolones containing an adamantane fragment were synthesized from adamantyl-substituted 1,3- and 1,4-diketones, ethyl 4-(1-adamantyl)-2-R-4-oxobutanoates (R = CN, Ac), and ethyl 2-(1-adamantylcarbonyl)-4-oxo-4-phenylbutanoate.     

Regiochemistry of the photostimulated reaction of the phthalimide anion with 1-iodoadamantane and tert-butylmercury chloride by the S(RN)1 mechanism

The photostimulated reaction of the phthalimide anion (1) with 1-iodoadamantane (2) gave 3-(1-adamantyl) phthalimide (3) (12%) and 4-(1-adamantyl) phthalimide (4) (45%), together with the reduction product adamantane (AdH) (21%). The lack of reaction in the dark and inhibition of the photoinduced reaction by p-dinitrobenzene, 1,4-cyclohexadiene, and di-tert-butylnitroxide indicated that 1 reacts with 2 by an S(RN)1 mechanism. Formation of products 3 and 4 occurs with distonic radical anions as intermediates. The photoinduced reaction of anion 1 with tert-butylmercury chloride (10) affords 4-tert-butylphthalimide (11) as a unique product. By competition experiments toward 1, 1-iodoadamantane was found to be ca. 10 times more reactive than tert-butylmercury chloride.     

Quantum-chemical study of the electronic structure of adamantane and the 1-adamantyl cation,anion, and radical

The spatial and electronic structures of the adamantane molecule (AdH), the 1-adamantyl radical (1-Ad^.), the 1-adamantyl cation (1-AD⁺), and the 1-adamantyl anion (1-Ad^–) have been calculated by the SCF-MO-LCAO method in the all-valence-electron MINDO approximation. The calculated heats of formation attest to the fact that the homolytic cleavage of the C-H bond is energetically most advantageous in the gaseous phase or in nonpolar inert solvents. The formation of a 1-Ad^–, H⁺ pair is associated with the largest expenditure of energy due to the large ionization potential of the hydrogen atom.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 3, pp. 357–360, May–June, 1989.     

Titanium dioxide photocatalysis of adamantane

TiO₂ photocatalysis of adamantane in oxygen equilibrated MeCN yields 1- and 2-adamantanol and adamantanone with limited degradation and preference for functionalization at the 1 position, particularly in the presence of silver salts. Oxidation in CH₂Cl₂ is less selective. The oxidation of cyclohexane and cyclododecane is slower. In N₂-flushed solutions with Ag⁺ as a sacrificial acceptor, products from the trapping of both 1-adamantyl radical (adamantyl methyl ketone) and cation (N-adamantylacetamide) are obtained. Furthermore, alkylation of an electrophilic alkene (isopropylydenmalononitrile) has been obtained, though in a low yield.     

[1+1]-cyclization of 4-(1-adamantyl)-2,6-diformylphenol with 1,3-bis(aminoalkyl)adamantanes

Selective [1+1]-cyclization of 4-(1-adamantyl)-2,6-diformylphenol with 1,3-bis(aminoalkyl)-adamantane under high dilution conditions in methanol was used to synthesize a new type of adamantine araliphanes, macrocyclic nitrogen-containing compounds with phenolic and adamantane fragments incorporated in the macroring. The [1+1]-cyclization reaction proceeds unusually to form, along with macrocyclic Schiff bases, methanol addition products at one of the N=CH groups of these compounds. The [1+1]-cyclization pattern is shown to depend on the reaction conditions and the structure of the starting diamine.     

Synthesis and properties of N-substituted aminofuroxans in the adamantane series

3-N, N-Disubstituted aminofuroxans in the adamantane series have been obtained by the oxidation of anti [1, (3-R-adamantyl) ]-amphi-glyoximes with excess K₃Fe(CN)₆ in the presence of the corresponding amines. Preparation of 3-amino and 3-methyl-amino-4-(1-adamantyl) furoxans requires initial synthesis of 2-(1-adamantyl)-2-hydroximinoacetonitrile oxide followed by addition of the corresponding amines and oxidation of the resulting glyoximes. Substituent positions in the furoxan ring were determined by PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1124–1127, August, 1988.     

Synthesis and characterization of aliphatic alpha-dithiones, di(1-adamantyl)- and di-tert-butylethanedithiones

2,3-Di(1-adamantyl)thiirene 1-oxide quickly reacted with Lawesson's reagent in CH2Cl2 at room temperature to provide di(1-adamantyl)ethanedithione (1) as thermally labile, violet crystals in 20% isolated yield. The use of CS2 as the solvent gave 1 in 46% isolated yield. The reaction in the presence of dimethyl acetylenedicarboxylate furnished dimethyl 4,5-di(1-adamantyl)-2,3-thiophenedicarboxylate in 51% yield. A tentative mechanism for the formation of 1 is proposed on the basis of the experimental observations. The structure of 1 was characterized on the basis of spectroscopic data (NMR, mass, IR, Raman, and UV/vis) and DFT calculations. 1 rearranged to 3,4-di(1-adamantyl)-1,2-dithiete quantitatively with kinetic parameters of DeltaH = 17.6 +/- 0.2 kcal mol-1, DeltaS = -23.0 +/- 0.7 cal K-1 mol-1, and DeltaG = 24.4 +/- 0.4 kcal mol-1. Peracid oxidation and Pt-complex formation of 1 are also reported.     

Carbocation-forming reactions in ionic liquids

A number of trifluoroacetates, mesylates, and triflates have been studied in ionic liquids. Several lines of evidence indicate that all of these substrates react via ionization to give carbocationic intermediates. For example, cumyl trifluoroacetates give mainly the elimination products, but the Hammett rho+ value of -3.74 is consistent with a carbocationic process. The analogous exo-2-phenyl-endo-3-deutero-endo-bicyclo[2.2.1]hept-2-yl trifluoroacetate gives an elimination where loss of the exo-hydrogen occurs from a cationic intermediate. 1-Adamantyl mesylate and 2-adamantyl triflate react to give simple substitution products derived from capture of 1- and 2-adamantyl carbocations by the residual water in the ionic liquid. The triflate derivative of pivaloin, trans-2-phenylcyclopropylcarbinyl mesylate, 2,2-dimethoxycyclobutyl triflate, the mesylate derivative of diethyl (phenylhydroxymethyl)-thiophosphonate, and Z-1-phenyl-5-trimethylsilyl-3-penten-1-yl trifluoroacetate all give products derived carbocation rearrangements (kDelta processes). anti-7-Norbornenyl mesylate gives products with complete retention of configuration, indicative of involvement of the delocalized 7-norbornenyl cation. 1,6-Methano[10]annulen-11-yl triflate reacts in [BMIM][NTf2] to give 1,6-methano[10]annulen-11-ol, along with naphthalene, an oxidized product derived from loss of trifluoromethanesulfinate ion. Analogous loss of CF3SO2- can be seen in reaction of PhCH(CF3)OTf. Ionic liquids are therefore viable solvents for formation of carbocationic intermediates via kC and kDelta processes.     

A facile synthesis of 3,4-homoadamantanediol via the reaction of 1-adamantyl triflate with carbon monoxide

The reaction of 1-adamantyl triflate ($\text{1}$) with carbon monoxide and adamantane catalyzed by triflic acid affords 3-hydroxy-4-homoadamantyl 1-adamantanecarboxylate ($\text{2}$) as a major product, which is easily converted to 3,4-homoadamantanediol ($\text{5}$) — a promising starting material for 3,4-bifunctional homoadamantane derivatives.     

Direct Clay-Catalyzed Friedel-Crafts Arylation and Chlorination of the Hydrocarbon Adamantane

Multiple chlorinations and arylations at the tertiary positions of adamantane are promoted by FeCl₃-doped K10 montmorillonite in CCl₄ or in aromatic solvents. The process, remarkably easy to implement, can be tailored to selective formation of monosubstituted 1-adamantyl derivatives or 1,3-disubstituted adamantanes. The process achieves alkylation at the meta- and para-positions of toluene leading to a purely statistical distribution and displays no substrate specificity in competition experiments between toluene and benzene.     

Thermodynamic parameters of adsorption of adamantane and its derivatives on graphitized thermal carbon black

The adsorption equilibrium constants for adamantane, 1-fluoro-, 1-chloro-, 1,3-difluoro-, 1,3-dichloro-, 1,3-dibromo-, and 1-hydroxyadamantane, and methyl 1-adamantyl ketone were determined by gas chromatography. The results were compared with molecular statistical calculations based on the known atomic-atomic potentials of the interaction of atoms of the sorbate molecule with the C atom of graphitized thermal carbon black (GTCB). The experimental adsorption heats exceed the calculated values by 3-10 kJ mol^-1. The reasons for this divergence are discussed. The changes in the adsorption entropy show that the molecules of the studied compounds form a layer of the ideal dimeric gas on the GTCB surface upon adsorption.     

Synthesis of 1,8-di(1-adamantyl)naphthalenes as single enantiomers stable at ambient temperatures

Single enantiomers of 1,8-di(1-adamantyl)naphthalenes were synthesized by the [4+2]cycloaddition reaction of 6-adamantylbenzyne and 2-adamantylfuran. The enantiomers were resolved by conversion into diastereomeric ketopinic acid esters. The absolute configuration was determined by X-ray analysis. Kinetic studies by CD revealed an enantiomerization barrier of 29 kcal mol(-1) for 1,8-(1-adamantyl)naphthalenes.     

含氨基的金刚烷桥头二取代化合物合成研究

采用金刚烷甲酸为原料,经溴代、叠氮化、库尔提斯重排、水解等四步反应合成了3-氨基-1-金刚烷醇(糖尿病药物中间体),总收率为34%;以金刚烷甲酸为原料,在无需卤素取代下,通过里特反应、水解反应合成了3-氨基-1-金刚烷甲酸盐酸盐(抗肿瘤药物中间体),总收率为73%.采用元素分析、红外光谱、质谱、核磁共振谱等手段对两种产物的进行了结构鉴定,分别提出了可能的反应机理.     

Aminophosphine–oxazoline and phosphoramidite–oxazoline ligands and their application in asymmetric catalysis

The synthesis of a novel series of aminophosphine–oxazoline and phosphoramidite–oxazoline is described. The efficacy of these aminophosphine–oxazoline ligands was investigated in the palladium catalysed asymmetric allylic alkylation of 1,3-diphenylprop-2-enyl acetate leading to a maximum of 38% ee at 64% conversion. Phosphoramidite–oxazoline ligands, however, gave ees of up to 87% at 71% conversion in the same reaction and also proved to be effective in the palladium catalysed asymmetric Suzuki coupling between 2-methylnaphthylboronic acid and 1-bromonaphthalene, leading to a maximum of 46% ee in 54% isolated yield at room temperature.