Synthesis of the first examples of p-bromodienone and transannular spirodienone calixarene derivatives

The first examples of p-bromodienone calixarene derivatives (6-7 and 9-10) have been obtained by treatment of 1,5-dihydroxy-hexaalkoxycalix[8]arenes 5 or tripropoxycalix[4]arene 8 with trimethylphenylammonium tribromide and a saturated solution of NaHCO₃. The first transannular spirodienone derivative 11 was only obtained in the presence of NaOH or using the KOH/I₂/PEG-200 oxidizing system.     

Direct alkenylation of arylamines at the ortho-position

Treatment of magnesium alkylidene carbenoids, which were generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride at −78 °C in toluene, with N-lithio arylamines gave ortho-alkenylated arylamines in moderate to good yields. The reaction was found to proceed in a highly stereospecific manner at the carbenoid carbon. This reaction offers a quite novel and direct alkenylation of arylamines at the ortho-position of the aromatic ring.     

The formylation of the upper-rims of thiacalixarenes: synthesis of the first tetra-formylated and the first meta-substituted thiacalix[4]arenes

The conventional Gross reaction for the formylation of the tetrapropoxythiacalix[4]arene using TiCl₄ affords the 18-(chloromethyl)-28-hydroxy-25,26,27-tripropoxythiacalix[4]arene substituted in the meta-position of the macrocycle. The p-tetraformyl-tetrapropoxythiacalix[4]arene, which is an interesting intermediate to the upper-rims functionalization of thiacalixarenes, was prepared with a very good yield using BuLi and N-formylpiperidine.     

Synthesis and in vivo biological activity of large-ringed calixarenes against Mycobacterium tuberculosis

A series of large-ringed calix[6,7,8]arene analogues have been synthesised and their affect against Mycobacterium tuberculosis in vivo established. In general, when p-phenylcalixarenes and tert-butylcalixarenes were not functionalised at the lower rim, low biological activities were observed. However on going from partially to fully lower rim pegylated calixarenes the anti-mycobacterial properties improved. The addition of cyanopropoxy groups at the lower rim gave rise to low activities, whereas the addition of acetate moieties interestingly had pro-TB effects. Two upper rim sulfonated calixarenes showed promising properties. In the course of this work, a high yielding procedure to synthesise p-phenylcalix[7]arene was also established.     

Regioselective ipso formylation of p-tert-butylcalix[4]arene

A convenient procedure for direct introduction of one formyl group into p-tert-butylcalix[4]arenes through ipso substitution is described.     

Preparation of p-nitrocalix[n]arene methyl ethers via ipso-nitration and crystal structure of tetramethoxytetra-p-nitrocalix[4]arene

Nitration of p-tert-butylcalix[n]arene methyl ethers under a variety of reaction conditions has been examined. It has been determined that amongst different nitration procedures adopted (AlCl₃/KNO₃, HNO₃/CH₃COOH, HNO₃/(CH₃CO)₂O, cerium(IV) ammonium nitrate/CH₃COOH), ipso-nitration with CH₃COOH/HNO₃ gives best yields of p-nitrocalixarenes and work up conditions. ipso-Nitration of tetramethoxytetra-p-tert-butylcalix[4]arene gives tetramethoxytetra-p-nitrocalix[4]arene as triclinic crystals with space group with a=9.102(3) Å, b=11.623(3) Å, c=18.368(3) Å and α=77.99(2)°, β=81.10(2)°, γ=73.37(2)°. Its conformation is partial cone and it forms an exocylic 1:1 complex with DMF.     

First examples of tetracyclic triterpenoids with a D:B-friedobaccharane skeleton. A tentative biosynthetic route

Baruol (1) and Leonal (2), first examples of tetracyclic triterpenes possessing a D:B-friedobaccharane skeleton, were isolated from Maytenus blepharodes and M. chiapensis, respectively. Their structures were established by spectroscopic analysis, molecular modeling studies and biogenetic background. The implication of the D:B-friedobaccharenyl cation in the biosynthetic route of baccharane and shionane skeletons is discussed. Baruol exhibited β-glucuronidase inhibitory activity, a target in the search for hepatoprotective agents.     

Synthesis of azepino[3,4b]indoles via the Plancher rearrangement

The reaction of benzyl 3-formylpiperidine-1-carboxylate and aryl hydrazines under standard Fisher Indole conditions followed by reductive work-up affords azepino[3,4b]indoles in moderate to good yields. The products are proposed to be derived via a Plancher rearrangement [(a) Plancher, G. Gazz. Chim. Ital. 1898, 28, II, 374; (b) Plancher, G. Atti. Accad.Lincei1900, 9, 5, 115; (c) Boyd-Barrett, H. S. J. Chem. Soc.1932, 321].     

Synthesis of Y-type hexaferrites via a soft mechanochemical route

Y-type (Ba₂Co₂Fe₁₂O₂₂) hexaferrite precursors have been prepared via a soft mechanochemical route from mixtures comprising BaCO₃, Co(OH)₂ and α-FeOOH. The mixture was activated with a multi-ring type mill for varying duration. The chemical and structural changes during grinding were examined in detail by XRD, DTA-TG, SEM, XPS and FTIR. During grinding, extended crystallinity loss or lattice disturbance was observed without an emersion of any new crystalline phases. At the same time, electronic states were changed toward the final product, fully crystallized Y-phase ferrite. Mechanical activation for only 1 h was sufficient to obtain a precursor for phase pure Y-type by subsequent heating in air at temperatures as low as 1000 °C. Development of plate-like anisotropy by using a precursor with prolonged milling was also observed. Magnetic permeability, μ′, was ca. 3 at 1 GHz, equivalent to the reported data, in spite of the lower firing temperature.     

Uptake of weathered p,p′-DDE by plant species effective at accumulating soil elements

Ten plant species previously shown to accumulate inorganic elements effectively from natural solids were grown under field conditions in p,p′-dichlorodiphenyldichloroethane (p,p′-DDE) contaminated soil. The plant species, which included rye, mustard, canola, vetch, pigeonpea, clover, peanut, and 3 cultivars of white lupin, represented both monocots and dicots, as well as two major families within the dicots: the Brassicaceae and the Fabaceae. The plants varied widely in their ability to phytoextract and translocate weathered p,p′-DDE. The percentage of contaminant phytoextracted ranged from 0.06% (white lupin) to 0.22% (clover, vetch), and the translocation factors (TF; contaminant concentration ratio of stems to roots) ranged from 0.04 (clover, white lupin) to 0.37 (canola). An inverse relationship exists between the amount of contaminant in the roots as measured by the root BCF (bioconcentration factor; dry weight contaminant concentration ratio of root to soil) and the TF. Duplicate mounds of each species were periodically amended with nitrogen (N), phosphorus (P), nitrogen and phosphorus together (N/P); a minus phosphorus treatment involved the addition of AlSO₄ to the soil prior to planting. The effect of nutrient regime on plant biomass, p,p′-DDE uptake and translocation, and inorganic element content varied greatly among the 10 plant species. For some species (rye, vetch, pigeonpea, clover, white lupin), reductions or non-significant changes in p,p′-DDE uptake were observed under the nutrient treatments and were not correlated with plant biomass effects. For mustard, canola, and peanut, the percentage of p,p′-DDE phytoextracted in the various treatments was more than doubled and was directly correlated with a two-fold increase in total plant biomass. Although it is generally assumed that fertilizer amendments will enhance the phytoremediation of organic and inorganic pollutants, the data here suggest that such effects are highly species specific and in some cases may actually decrease remediation potential.     

Ab initio study of the mechanism of the formation of p-rosolic acid from trifluoromethoxybenzene under HF/Lewis acid conditions

The mechanism of the formation of p-rosolic acid from trifluoromethoxybenzene under HF/Lewis acid conditions was studied using ab initio methods. A series of cationic intermediates is initiated by the expulsion of a fluorine atom of trifluoromethoxybenzene with anomeric assistance of the trifluoromethoxy oxygen. The resulting difluorocarbonium ion is attacked by a second trifluoromethoxybenzene to generate the first carbon-carbon bond on what will be the central carbon of p-rosolic acid. Elimination of phenol results in the formation of cationic intermediate 4 which is susceptible to carbon-alkylation by the same phenol to form the second carbon-carbon bond. Attack on subsequent difluorocarbonium ions by trifluoromethoxybenzene strips trifluoromethyl groups from the downstream intermediates, eventually leading to p-rosolic acid, and continues the generation of 4, each of which initiate a fresh mechanistic series toward another p-rosolic acid molecule.     

Ring expansion of 11H-benzo[b]fluorene-11-methanols and related compounds leading to 17,18-diphenyldibenzo[a,o]pentaphene and related polycyclic aromatic hydrocarbons with extended conjugation and novel architectures

Condensation between 7-(1,1-dimethylethyl)-13-phenyl-8H-indeno[2,1-b]phenanthrene and paraformaldehyde produced the corresponding 9-fluorenylmethanol derivative, which on treatment with P₂O₅ to promote a Wagner-Meerwein rearrangement for ring expansion furnished 14-phenyldibenzo[a,j]anthracene in 88% yield. Similarly, 17,18-diphenyldibenzo[a,o]pentaphene possessing a helical twist and bearing two phenyl substituents at the most sterically congested C17 and C18 positions and other related compounds were likewise synthesized. Subsequent intramolecular arylation reactions involving the phenyl substituents produced polycyclic aromatic hydrocarbons with novel architectures.     

Total synthesis of rhein and diacerhein via a directed ortho metalation of an aromatic substrate

An efficient total synthesis of rhein and diacerhein has been accomplished by relying on a remarkable regioselective directed ortho metalation (DOM) followed by a one-pot two step addition-cyclization reaction, generating phthalide 5 intermediate efficiently.     

New soluble aromatic polyamides containing ether linkages and laterally attached p-terphenyls

Two series of new polyamides containing flexible ether linkages and laterally attached side rods (3a-i and 4a-i) were synthesized from 2^′,5^′-bis(4-aminophenoxy)-[1,1^′;4^′,1^″]terphenyl (1a) and 2^′,5^′-bis(4-amino-2-trifluoromethylphenoxy)-[1,1^′;4^′,1^″]terphenyl (1b), respectively, with various aromatic dicarboxylic acids by the direct phosphorylation polycondensation. The polymers were produced with high yields and moderate to high inherent viscosities (0.41-0.97 dl/g) that corresponded to weight-average molecular weights (by size exclusion chromatography) of 47,000-65,000. Except for some polyamides that derived from rigid diacids, the obtained polyamides were readily soluble in aprotic polar solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc), and could afford flexible and tough films via solvent casting. The polymer films cast from DMAc solutions possessed tensile strengths of 85-106 MPa and initial moduli of 1.82-2.96 GPa. These polyamides showed glass-transition temperatures (T_g) in the range of 206-263 °C (by DSC) and softening temperatures (T_s) in the range of 211-253 °C (by TMA). Decomposition temperatures (T_d) for 10% weight loss all occurred above 400 °C (by TGA) in both nitrogen and air atmospheres. The polyamides 4a-i derived from trifluoromethyl-substituted diamine 1b generally showed a higher solubility, T_g and T_s but lower thermal stability as compared to the analogous polyamides 3a-i based on diamine 1a.     

Microwave-assisted one-pot synthesis of benzo[b][1,4]thiazin-3(4H)-ones via Smiles rearrangement

The synthesis of benzo[b][1,4]thiazin-3(4H)-one derivatives in a simple and efficient method from the one-pot reaction of substituted 2-chlorobenzenthiols, chloroacetyl chloride, and primary amines via Smiles rearrangement under microwave irradiation gave high yields (65-92%) of the products with short reaction time (15-20 min).     

p-Sulfonic acid calixarenes as efficient and reusable organocatalysts for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones/-thiones

A new and efficient methodology is proposed for obtaining 3,4-dihydropyrimidin-2(1H)-ones/-thiones through Biginelli reactions. It is based on the use of less than the stoichiometric amount of p-sulfonic acid calixarenes as organocatalysts. A number of aromatic aldehydes as well as urea or thiourea can be employed for successfully synthesizing the corresponding Biginelli adducts. The described methodology is devoid of metal-containing catalysts, which in turn is very attractive for safely producing 3,4-dihydropyrimidin-2-(1H)-ones/-thiones of pharmacological interest. In addition, the catalyst efficiency is not compromised after its successive use in reactions. This is the first report about the application of calixarenes as catalysts in the multicomponent Biginelli reaction.     

NMR J-based analysis of nitrogen-containing moieties and application to dysithiazolamide, a new polychlorinated dipeptide from Dysidea sp.

The methodology of J-based analysis applied to 1,3-methylcarboamido systems allowed us to deduce the relative configurations of the two leucine-like fragments of a new tetrachloro amino acid derivative dysithiazolamide, which was isolated from an unidentified sponge of the genus Dysidea. Furthermore, the absolute configuration was also proposed by comparison with analogous systems.     

Synthesis of N,N′-bis and N,N,N′,N′-tetra-[(3,5-di-substituted-1-pyrazolyl)methyl]para-phenylenediamines: new candidate ligands for metal complex wires

A series of tridentate ligands N,N-bis-[(di-substituted-1-pyrazolyl)methyl]arylamines 2-3a,b and benzylamine 4a,b, tetradentate N,N′-bis-[(di-substituted-1-pyrazolyl)methyl]para-phenylenediamines 7a,b and hexadentate N,N,N′,N′-tetra-[(di-substituted-1-pyrazolyl)methyl]para-phenylenediamines 8a,b has been prepared in good yield by condensation of arylamines, benzylamine or para-phenylenediamine with N-hydroxymethyl disubstituted pyrazoles 1a,b. The synthesis and characterisation of these various polydentate ligands are described.     

An efficient route for the construction of cyclopenta[b]quinoline derivatives via intramolecular cyclopropanation

A one-pot process to introduce diazoacetoacetate functionality into quinoline was identified with excellent yield and regioselectivity. An intramolecular cyclopropanation of the resulting adducts gave tetracyclic cyclopenta[b]quinoline derivatives in nearly quantitative yields. A synthetic utility of the tetracyclic derivatives was examined by a simple ring opening reaction to afford cyclopenta[b]quinoline in a good yield.     

Synthesis of enantiopure (S)-7-hydroxy-3-amino-3,4-dihydro-2H-1-benzopyran en route to (+)-scyphostatin

(S)-7-Hydroxy-3-amino-3,4-dihydro-2H-1-benzopyran, a key synthetic intermediate towards the total synthesis of (+)-scyphostatin, has been prepared in >98% ee. Key synthetic steps were (i) the oxidative dearomatization of an l-tyrosine derived phenol, (ii) the transformation of the resulting p-quinol acetate to the corresponding resorcinol upon exposure to Thiele reaction conditions and, (iii) the direct formation of the benzopyran ring upon treatment of an N-Boc protected 4-(2-acetoxybenzyl)oxazolidin-2-one with sodium methoxide.