Synthesis of spirane-bridged rigidified oxalkyl cyclopentadienyl ligands

Methods for the preparation of constrained spirane-bridged oxalkyl indenyl ligands are described. The cis,cis-α,α′-spirane derivatives were synthesised in several steps from spiro[4.4]nonane-1,6-dione. Carbylation was achieved by Wittig methenylation. A subsequent stereoselective hydroboration by 9-BBN followed by peroxide treatment furnished the corresponding cis-methanol. Further manipulations provided the cis-carboxylic ester, which in a double Grignard reaction with α,α′-dichloro-o-xylene, furnished the corresponding indenyl derivative. The final products were cis,cis-α-(2-indenyl)-α′-(methoxy or methoxymethyl)spiro[4.4]nonanes.     

Spirooxindoles: reaction of 2,6-diaminopyrimidin-4(3H)-one and isatins

A simple and efficient cyclocondensation reaction of 2,6-diaminopyrimidin-4(3H)-one and isatins for the synthesis of spiro[pyrimido[4,5-b]quinoline-5,5′-pyrrolo[2,3-d]pyrimidine] and spiro[indoline-pyrido[2,3-d:6,5-d′]dipyrimidine] derivatives is reported.     

Facile synthesis of spiro[benzo[e]indole-2,2′-piperidine] derivatives and their transformation to novel fluorescent scaffolds

The reaction of azaheterocyclic enamines with acrylamide was employed for the preparation of novel fluorescent scaffolds possessing a benzo[e]indoline moiety. Reaction of 3-substituted 2-methylidene-1H-benzo[e]indole with acrylamide gave rise to spiro[benzo[e]indole-2,2′-piperidin]-6′-ones. Ring opening reactions of the latter spiro compounds were investigated. Benzo[e]indoline derivatives possessing 2-(3-carbamoylpropyl), 2-[3-(ethoxycarbonyl)propyl] and 2-(4-aminobutyl) side chains were synthesised. The optical properties of the benzo[e]indoline derivatives were studied by UV-vis and fluorescence spectroscopy.     

Synthesis and transformations of [1,2-O-isopropylidene-α-d-erythro (and α-d-ribo)furanose]-3-spiro-3′-(4′-amino-5′H-2′,3′-dihydroisothiazole-1′,1′-dioxide) derivatives

The carbanion-mediated sulfonamide cyclisations (CSIC protocols) of glyco-α-sulfonamidonitriles derived from readily available uloses 1A and 1B have been investigated using different bases (potassium carbonate, cesium carbonate, LDA and n-BuLi). As a result, a series of enantiomerically pure [1,2-O-isopropylidene-α-d-erythro (and α-d-ribo)furanose]-3-spiro-3′-(4′-amino-5′H-2′,3′-dihydroisothiazole-1′,1′-dioxide) derivatives have been prepared and isolated in good yields.     

Total syntheses of (±)-α-acorenol, β-acorenol, α-epi-acorenol and β-epi-acorenol via an Ireland ester Claisen rearrangement and RCM reaction sequence

Total syntheses of (±)-α- and β-acorenols and (±)-α- and β-epi-acorenols, spiro[4.5]decane sesquiterpenes, isolated from the western Australian sandalwood oil, have been accomplished employing a combination of Ireland ester Claisen rearrangement and RCM reactions for an efficient construction of the spiro[4.5]decane present in acoranes.     

Simple construction of fused and spiro nitrogen/sulfur containing heterocycles by addition of thioamides or thioureas on cycloalkenyl-diazenes: examples of click chemistry

New 1-cycloalkenyl-1-diazenes have been obtained in good yields from cyclic β-ketoesters and hydrazine derivatives. They furnished new cycloalkyl[d][1,3]thiazolines with thioamides or new spirocycloalkyl-thiazolinones with thioureas. Moreover they gave, with imidazolidine-2-thione and tetrahydropyrimidine-2-thione, new and interesting spiro[cycloalkyl-1,2′-imidazo[2,1-b][1,3]thiazole] or spiro[cycloalkyl-1,2′-[1,3]thiazolo[3,2-a]pyrimidine] derivatives, respectively. Cycloalkyl[d][1,3]thiazolines were useful for the further preparation of unknown thia-triaza-tricyclo derivatives. Novel hexahydro-1,3-benzothiazoles have been achieved by reaction of N,N′-dialkylthioureas on N-1-phenyl-2-(1-cyclohexenyl)-1-diazene-1-carboxyamide. The acidic hydrolysis of spirocycloalkyl-thiazolinones produced 2-imino-5-(ω-carboxyalkyl)-4-thiazolidinones.     

Asymmetric synthesis of spiro 2-pyrrolidin-5-ones, 2-piperidin-6-ones and 1-isoindolin-3-ones. Part 2: N-Acyliminium ion cyclisations with an internal alkene nucleophile

Chiral non-racemic bicyclic and tricyclic oxylactams obtained in two steps from N-(2-hydroxy-1(R)-phenylethyl)-succinimide and phthalimide are cyclised diastereoselectively in formic acid to give spiro[cyclohexane-1,2′-pyrrolidin]-5-ones and spiro[cyclohexane-1,1′-isoindolin]-3-ones, respectively.     

Synthesis of spiro[benzopyrazolonaphthyridine-indoline]-diones and spiro[chromenopyrazolopyridine-indoline]-diones by one-pot, three-component methods in water

The synthesis of spiro[benzo[h]pyrazolo[3,4-b][1,6]naphthyridine-7,3′-indoline]-2′,6(5H)-diones and spiro[chromeno[4,3-b]pyrazolo[4,3-e]pyridine-7,3′-indoline]-2′,6(6aH,10H)-diones via a one-pot, three-component reaction of 4-hydroxycoumarin or 4-hydroxy-1-methylquinolin-2(1H)-one, isatins and 1H-pyrazol-5-amines in water is reported.     

A novel domino condensation–intramolecular nucleophilic cyclization approach towards annulated thiochromenes

A one-pot protocol towards previously unreported derivatives of thiochromeno [2′,3′:4,5] imidazo[2,1-a]isoquinoline via a domino reaction of isoquinoline-derived iminium salts and α-mercapto benzaldehydes is elaborated.     

A new synthesis, including asymmetric synthesis, of spiro[4.n]alkenones from three components: cyclic ketones, chloromethyl p-tolyl sulfoxide, and acetonitrile; and a formal total synthesis of racemic acorone

1-Chlorovinyl p-tolyl sulfoxides were synthesized from several kinds of cyclic ketones and chloromethyl p-tolyl sulfoxide in good yields. Treatment of the 1-chlorovinyl p-tolyl sulfoxides with cyanomethyllithium at −78°C to room temperature gave spirocyclic enaminonitriles in high yields. Acidic treatment of the enaminonitriles afforded spiro[4.n]alkenones in good yields. By using an unsymmetrical cyclic ketone, α-tetralone, and optically active chloromethyl p-tolyl sulfoxide, this procedure afforded enantiomerically pure spiro[4.5]decenone in good yield with excellent asymmetric induction from the sulfoxide chiral center. By using this method a formal total synthesis of a racemic spirocyclic sesquiterpene, acorone, was realized.     

Carbohydrate-derived spiroketals: stereoselective synthesis of di-d-fructose dianhydrides

A one-pot synthesis of di-d-fructose dianhydrides (DFAs) having the 1,6,9,13-tetraoxadispiro[4.2.4.2]tetradecane and 1,7,10,15-tetraoxadispiro[5.2.5.2]hexadecane skeleton has been accomplished. The methodology relies on the ability of per-O-protected 1,2-O-isopropylidene β-d-fructofuranose and β-d-fructopyranose derivatives to undergo a tandem acetal cleavage-intermolecular glycosylation-intramolecular spiroketalization process by reaction with suitable acid promoters, such as boron trifluoride etherate or trifluoromethanesulfonic acid, in apolar organic solvents. Spirocyclization proceeds then under irreversible reaction conditions to give binary mixtures of di-d-fructofuranose (α,α and α,β diastereomers) or di-d-fructopyranose 1,2′:2,1′ dianhydrides (β,β and α,β), respectively, the stereochemical outcome being dependent on the non-participating or participating character of the protecting groups. Thus, benzylated and allylated derivatives afford, preferentially, the non-symmetric DFAs (α,β), with diastereomeric excess up to 92%. In contrast, the use of participating benzoyl groups favours the C₂-symmetric diastereomer in both series.     

Novel four-component route to the synthesis of spiro[indoline-3,4′-pyridine]-3′-carboxylate derivatives

An effective route to spiro[indoline-3,4′-pyridine]-3′-carboxylate derivatives is described. This involves reaction of isatin, 1-phenyl-2-(1,1,1-triphenyl-λ⁵-phosphanylidene)-1-ethanone, and benzylamine derivatives or aliphatic amines in the presence of alkyl acetoacetate (1,3-dicarbonyl compounds) in dry methanol under reflux conditions. The reactive 1:1 enaminone, which is obtained from the addition of the amine to 1,3-dicarbonyl compound, adds to the α,β-unsaturated ketone, which is formed from the reaction of isatin and 1-phenyl-2-(1,1,1-triphenyl-λ⁵-phosphanylidene)-1-ethanone, to produce the alkyl 1′-benzyl-2′-methyl-2-oxo-6′-phenyl-1′H-spiro[indoline-3,4′-pyridine]-3′-carboxylate derivatives in excellent yields.     

Elaboration and structural studies of cyclo 1:1-[α/α-N-amino]mers

In order to investigate the ability of self-organization of the alternance of α-amino and α-N-amino-acids the synthesis of cyclo 1:1-[α/α-N-amino]mers has been achieved by an iterative sequence of deprotection and coupling reactions followed by a macrocyclization step. The self-assembling of N-amino deprotected cyclo-oligomers has been characterized using X-ray diffraction experiments and FT-IR analysis.     

The interactions between some N-acetyl-N′-methyl-l-α-amino acid amides and urea in water at 298.15 K

The enthalpies of solution of N-acetyl-N′-methylglycinamide, N-acetyl-N′-methyl-l-α-alaninamide, N-acetyl-N′-methyl-l-α-leucinamide and N-acetyl-N′-methyl-l-α-serinamide have been measured in water and in aqueous urea solutions with molalities from 0.25 to 3.0 mol kg⁻¹ at 298.15 K. From these data the standard dissolution enthalpies of amides in aqueous urea solutions have been determined. The results have been treated according to McMillan-Mayer's theory in order to obtain the enthalpic coefficients of the interactions between amino acid derivatives and urea molecules. The obtained parameters were compared with the hydrophobic scale for the amino acid side chains.     

Towards peptide versions of Cram's host-guest chemistry: the synthesis of C-disubstituted glycines with binaphthol-based crowned side-chains

Dietherification of the hydroxy groups of various α,α-disubstituted α-amino acids or their precursors, possessing either an achiral frame derived from α-hydroxymethylserine, or a 2,2′,6,6′-tetrasubstituted biphenyl frame with only an axial chirality, or a frame with α-carbon chirality derived from α-methyl-(L)-DOPA, using (R)-2,2′-bis-(5-tosyloxy-3-oxa-1-pentyloxy)-1,1′-binaphthyl as alkylating agent, gave a new series of amino acids bearing binaphthol-based crown-ethers, as building blocks for the construction of short-chain peptide helices with topologically well-localized receptors.     

An efficient synthesis of novel spiro[[8H]indeno[2,1-b]-thiophene-8,9′-fluorene] building block for blue light-emitting materials

We have developed efficient synthetic routes to obtain a novel building block spiro[[8H]indeno[2,1-b]thiophene-8,9′-fluorene] (SITF), a monothiophene-containing spirobifluorene analogue, and constructed blue light-emitting materials, including 2′,7′-bis([1,1′-biphenyl]-4-yl)-spiro[indeno[2,1-b]thiophene-8,9′-fluorene] (BBP-SITF) and 2′,7′-bis(9,9′-spirobifluoren-2-yl)spiro[[8H]indeno[2,1-b]-thiophene-8,9′-fluorene] (BSBF-SITF). BSBF-SITF has shown to be a stable blue light-emitting material with high PL quantum efficiency (89%) and unique regioselective feature at the C2 of thiophene, which indicate that BSBF-SITF will be useful for constructing complicated optoelectronic systems.     

Clerodane diterpenoids from Microglossa angolensis

Two new diterpenoids, 6β-(2-methylbut-2(Z)-enoyl)-3α,4α,15,16-bis-epoxy-8β,10βH-ent-cleroda-13(16),14-dien-20,12-olide and 10β-hydroxy-6-oxo-3α,4α,15,16-bis-epoxy-8βH-cleroda-13(16),14-dien-20,12-olide, together with the known β-amyrin, spinasterol, 5,7-dihydroxy-3,8,3′,4′-tetramethoxyflavone and 5,7-dihydroxy-3,8,3′,4′,5′-pentamethoxyflavone have been isolated from the aerial parts of Microglossa angolensis Oliv. et Hiern (Compositae). The structures were elucidated on the basis of spectral studies and comparison with published data.     

Stereocontrolled spirocyclization of exo-glucal derivatives for stereodivergent synthesis of spiro[5.5]ketals

This Letter describes a stereoselective synthetic approach to spiro[5.5]ketals from the exo-glucals, constructed from 1-(4-hydroxyalkylidene)-1,5-anhydro-d-glucitol, by spirocyclization based on intramolecular α- and β-selective glycosylation. Stereodivergent synthesis of both α- and β-glucoside of spiro[5.5]ketals was attained by combination of chiral d-glucopyranose environment and C-4′ chiral center on the side chain.     

A new synthetic procedure to spiro[cyclohexane-1,3′-indoline]-2′,4-diones

A new synthetic pathway to spiro[cyclohexane-1,3′-indoline]-2′,4-diones was found starting from 3-chloromethylene-2-indolones 1 and Danishefsky's diene 2. Their synthesis consists of several steps involving the formation of the cycloadducts, the 6-chloro-4-trimethylsilyloxy-2-methoxyspiro[cyclohex-3-en-1,3′-indolin]-2′-one derivatives, transformed into spiro[cyclohexa-2,5-dien-1,3′-indoline]-2′,4-diones via 6-chloro-spiro[cyclohex-2-en-1,3′-indoline]-2′,4-dione intermediates. The reduction of spiro[cyclohexa-2,5-dien-1,3′-indoline]-2′,4-diones gave spiro[cyclohexane-1,3′-indoline]-2′,4-diones 7. Using a ‘one pot reaction’, starting from 1 and 2, compounds 7 were obtained in satisfactory overall yield.     

Organometallic compounds : XII. stereochemical interconversion reactions between 1,1′−bis(α-hydroxyalkyl)ferrocenes and 7-oxa[3]ferrocenophanes

Meso and racemic isomers of 1,1′-bis(α-hydroxyalkyl)ferrocene derivatives, and trans and cis isomers of 7-oxa[3]ferrocenophanes have been isolated. The configurations of these isomers have been determined both by spectroscopy and from their reaction behavior. It has been found that the ring-closure and ring-opening interconversion reactions between 1,1′-bis(α-hydroxyalkyl)ferrocenes and 7-oxa[3]ferrocenophanes are stereospecific. PMR spectra of the diols and ethers have been examined at 100 MHz in CF₃COOH, and the existence of α-[1′-(α-hydroxyalkyl)ferrocenyl]carbonium ions has been demonstrated in this acid. A mechanism for the various interconversion reactions is proposed on the basis of their stereospecific reactivity and from the PMR spectra of the carbonium ions.