An easy access to gamma-lactone-fused cyclopentanoids

The tricyclic alpha-keto hemiacetals 3a,b and 8a-d obtained from ruthenium-catalyzed oxidation of tetrahalonorbornyl derivatives possessing a pendant hydroxymethyl group were cleaved using Pb(OAc)(4) or alkaline H(2)O(2) to give gamma-lactone-fused cyclopentane derivatives 5a,b and 9a-d. The alpha-keto hemiacetal 3b has also been elaborated to spiroepoxide derivative 25. The stable hydrate 4 formed from ruthenium-catalyzed oxidation of acrolein adduct 10 furnished an intramolecular hemiacetal 11 upon cleavage with Pb(OAc)(4). The alpha-halo ester moiety in 5a was transformed smoothly in a highly regio- and stereoselective manner to alpha-hydroxy esters through a lactone-assisted intermediate to furnish 18.     

An easy access to halogenated and non-halogenated spiro-hexadienones

We describe an improved protocol for the synthesis of spiro-hexadienones from Morita–Baylis–Hillman adducts. Solvent modification and temperature resulted in a significant increase in the yield. This protocol was used to synthesize mono- and dibrominated spiro-hexadienones in good overall yields. This report is the first to describe the synthesis of halogenated spiro-hexadienones from Morita–Baylis–Hillman adducts.     

Organoallylaluminum reagents promote easy access to trihalomethyl triazolyl homoallylic alcohols analogous to rufinamide

The results of allylation reactions employing allylaluminum reagents are described for 5-substituted (2,6-difluorobenzyl)-4-trifluoro(chloro)acetyl-1H-1,2,3-triazoles (1), in which the 5-substituents are H, Me, and Ph. The allylating reagents were generated in situ by the catalytic insertion of aluminum into allyl and crotyl bromides (2), in order to furnish a new series of twelve trihalomethyl triazolyl homoallylic alcohols (3) at yields of up to 94%. The excellent reactivity of these organoallyl reagents is highlighted as an economical alternative to the indium-mediated reactions to produce homoallylic alcohols, which are important building blocks in organic synthesis.     

An easy access to 7-methyl-2-naphthalenecarbonitrile

A practical and cost-effective procedure has been developed for the synthesis of 7-methyl-2-naphthalenecarbonitrile, the precursor of the anticoagulant agents YM-60828 or YM-96765. This new route generates the key intermediate in only two steps from readily available 3-cyanopropionaldehyde dimethyl acetal and m-tolualdehyde, without requiring chromatographic purification. The synthesis involves condensation of the cyano derivative with the aldehyde and subsequent cyclodehydration.     

Nitrobutadienes as powerful benzannulating agents: An unprecedented easy access to rare nitroindoles

We report herein an original protocol to the indole nucleus, which could contribute to significantly expand the synthetic access to a heterocyclic moiety of undeniable paramount importance. The protocol consists in the construction of the benzene ring onto a pyrrole (benzannulation) starting from 2,3-dinitro-1,3-butadienes. This appealing, metal-free process characterized by high atom economy and mild reaction conditions allows to synthesize indoles possessing nitro group(s) on the benzene ring: a result which cannot be likewise easily obtained by exploiting most common pathways such as functionalization of a preformed indole or heteroannulation of a suitable benzene derivative. From a mechanistic point of view, a stepwise, ionic process is suggested by the identification of a pivot dihydroindole intermediate whose interception facilitates some selectivity in the preparation of different nitroindoles.     

An easy access to unsymmetric trisubstituted methane derivatives (TRSMs)

A new series of unsymmetric trisubstituted methane derivatives (TRSMs) has been synthesized through Friedel-Crafts alkylation of aromatic nucleophiles using acid-sensitive heteroaryl carbinols.     

Nucleophilic addition of arylmethylzinc reagents (ArCH2ZnCl) to formaldehyde: An easy access to 2-(hetro)arylethyl alcohols

The selective addition of arylmethylmagnesium halides with formaldehyde giving arylethyl alcohols is extremely challenging. To circumvent the difficulties, in the current communication, we have reported on the nucleophilic addition of benzyl zinc reagents derived from inexpensive and abundant benzyl chlorides to paraformaldehyde. The reaction investigated herein is hitherto unknown and was found to be selective, operationally simple, atom- and step-economical and high yielding to deliver phenethyl alcohols utilized as key perfumery ingredients in 60–83% yields. After successful establishment of the reaction condition, the reaction was also scaled up successfully to deliver a large-scale preparation of the phenethyl alcohol.     

Synthesis of 5-substituted-3,4-dihydroxycyanopyrrolidines. An easy access to polyhydroxyprolines

A novel procedure for the synthesis of cyanopyrrolidines is presented. Starting from conveniently functionalized d-ribose, d-mannose, d-(l)-arabinose, the compounds were efficiently synthesised in four steps in overall good yields. Transformation into proline derivatives and preliminary evaluation of these derivatives in organocatalysis is also described.     

An easy access to unsymmetrically substituted 4,4′-bi-1,2,3-triazoles

A convenient synthesis of 4-alkynyl-1,2,3-triazoles and novel unsymmetrically substituted 4,4′-bi-1,2,3-triazole derivatives has been devised starting from easily available 1-trimethylsilyl-1,3-butadiyne. The starting compound was reacted with several azides, leading to 4-(silylalkynyl)-1,2,3-triazoles, which were easily transformed into 4-arylalkynyl-1,2,3-triazoles by a Pd catalyzed coupling reaction with aryl halides, or into novel 4,4′-bi-1,2,3-triazole derivatives by a subsequent cyclization reaction with azides.     

The charge-transfer motif in crystal engineering. Self-assembly of acentric (diamondoid) networks from halide salts and carbon tetrabromide as electron-donor/acceptor synthons

Unusual strength and directionality for the charge-transfer motif (established in solution) are shown to carry over into the solid state by the facile synthesis of a series of robust crystals of the [1:1] donor/acceptor complexes of carbon tetrabromide with the electron-rich halide anions (chloride, bromide, and iodide). X-ray crystallographic analyses identify the consistent formation of diamondoid networks, the dimensionality of which is dictated by the size of the tetraalkylammonium counterion. For the tetraethylammonium bromide/carbon tetrabromide dyad, the three-dimensional (diamondoid) network consists of donor (bromide) and acceptor (CBr(4)) nodes alternately populated to result in the effective annihilation of centers of symmetry in agreement with the sphaleroid structural subclass. Such inherently acentric networks exhibit intensive nonlinear optical properties in which the second harmonics generation in the extended charge-transfer system is augmented by the effective electronic (HOMO-LUMO) coupling between contiguous CBr(4)/halide centers.     

Photoreductive cyclization of unsaturated aldehydes : An easy access to spiranic molecules

The photoreductive cyclization of ω-unsaturated aldehydes is an efficient process which leads to substituted cycloalkanols. This process is used as a convenient approach to spiranic molecules.     

An easy access to functionalized allyl dithiocarbamates from Baylis-Hillman adducts in water

A facile and direct highly stereoselective synthesis of [E]- and [Z]-allyl dithiocarbamates has been accomplished from acetates of Baylis-Hillman (BH) adducts in catalyst-free one-pot three-component coupling reactions of carbon disulfide and amine in water under a mild and green procedure with high yields. The reaction pathway involves the nucleophilic displacement (SN2′) of BH acetates by dithiocarbamate anions. The utility of these allyl dithiocarbamates has also been demonstrated in heterocyclic chemistry. © 2009 Elsevier Science. All rights reserved     

First-principles determinations and investigations of the electronic absorption and third-order polarizability spectra of electron donor-acceptor chromophores tetraalkylammonium halide/carbon tetrabromide

Calculations on donor-acceptor molecular pairs of tetraalkylammonium halide/carbon tetrabromide complexes are provided to investigate structure/property-related linear and nonlinear optical properties by using the time-dependent density functional theory technique coupled with the sum-over-states method. The calculated energies of the first allowed electronic transition decrease, and the nonresonant third-order polarizabilities at the THG, EFISHG, and DFWM optical processes increase progressively from [DBU-H+Br-.CBr(4) to [NPr(4)Br.CBr(4)] to [NMe(4)Br.CBr(4)]. The obtained electronic absorption spectra show a progressive red shift with increasing donor strength from Cl to I for [NR(4)h.CBr(4)] (h = Cl, Br, and I). The charge transfers from the halogen donor to the carbon tetrabromide acceptor make significant contributions to the electronic absorption spectra in the low-energy zone and the third-order polarizabilities in the nonresonant frequency region. The counterion indirectly affects the electronic absorption and third-order polarizability spectra through the interactions between the donor and acceptor.     

An easy access to (S)-pyrrolidinones and -pyrrolidines from chiral benzylic malonates

From chiral benzylic malonic acid esters (R)-(+)-4, available with high enantiomeric excesses by enzymatic hydrolysis (PLE acetonic powder), enantiomerically enriched pyrrolidinones 1 and pyrrolidines 2 were prepared. This rapid and competitive method was developed via enol ether formation, and subsequent one-pot cyclisation, in good overall yield.     

Electronic origin for enhanced nonlinear optical response of complexes from tetraalkylammonium halide and carbon tetrabromide: electrostatic potentials of intermolecular donor-acceptor dyads

Electronic origin for nonresonant enhancement of nonlinear optical response in the complexes formed from tetraalkylammonium halide and carbon tetrabromide is provided in view of electrostatic potentials of intermolecular donor (halide ion)-acceptor (CBr(4)). The calculated electrostatic potentials of donor-acceptor range from -4.83 to -7.70 kcal mol(-1) and show a decreasing order of [Et(4)Cl(-)Br] > [Et(4)Br(-)Br] congruent with [Et(4)I(-)Br] > [Bu(4)Br(-)Br]. The calculated second-order susceptibilities of solid complexes are in an increasing order of [NEt(4)ClCBr(4)] < [NEt(4)BrCBr(4)] congruent with [NEt(4)ICBr(4)] < [NBu(4)BrCBr(4)C(3)H(6)O]. It has been shown that the donor/acceptor dyads make the exclusive contribution to nonlinear optical response. A large size of halide or tetraalkylammonium ion results in a small electrostatic potential and large nonlinear optical response in these charge-transfer complexes. It indicates that a small supermolecular interaction will create a large nonlinear optical response, and it gives a clue to design the molecular complexes with large non-linear optical susceptibility.     

An easy access to spiroannulated glyco-oxetane, -thietane and -azetane rings: synthesis of spironucleosides

The key intermediate 11 derived from d-glucose and possessing bis-mesylmethyl (MsO·CH₂-) functionality at C-4, was used to generate spirocycles 12, 13 and 15 via one-step procedures. The spirocompounds 12 and 13 were subsequently converted into the corresponding spironucleosides 24 and 26 in good yield using Vorbrüggen reaction conditions.     

Haems as potential reagents for carbon monoxide

A study of the potential of a myoglobin model system based on dipiperidyltetraphenylporphinatoiron(II) for the spectrophotometric determination of carbon monoxide is reported. At room temperature, oxygen does not bind strongly at the iron centre and does not interfere. Nitric oxide, hydrogen sulphide and carbon dioxide interfere and must be removed before the determination if present in significant amounts. The main disadvantage of this novel method is the low sensitivity (about 300 ppm CO). Possible means of modifying the system to enhance the sensitivity and to further reduce the number of interfering species are discussed.