Sequential Baylis-Hillman reaction and radical cyclization of furanose derivatives: expeditious approach to enantiopure benzo-fused nine-membered oxacycles

A regioselective 9-endo-trig aryl radical cyclization of d-glucose derived diastereomeric Baylis-Hillman reaction products with Bu₃SnH led to highly functionalized tricyclic benzannulated ethers incorporating cis- and trans-9,5 bicyclic systems in good yields. Degradation of one of the products afforded an enantiopure multifunctionalized benzoxonine derivative.     

Synthetic Applications of the Baylis–Hillman Reaction: Simple and Convenient Synthesis of Five Important Insect Pheromones

A simple and convenient synthesis of five important insect pheromones by means of Baylis–Hillman adducts is described, i.e., of (2E,4S)‐2,4‐dimethylhex‐2‐enoic acid ( 1 ), a mandibular‐gland secretion of the male carpenter ant in the genus Camponotus, of (+)‐(S)‐manicone ( 2 ) and (+)‐(S)‐normanicone ( 3 ), two mandibular‐gland constituents of Manica ants, and of (+)‐dominicalure‐I ( 6 ) and (+)‐dominicalure‐II ( 7 ), two aggregation pheromones of the lesser grain borer Rhyzopertha dominica (F). For the first time, the potential of the Baylis–Hillman chemistry for the stereoselective synthesis of trisubstituted olefins was successfully applied to the synthesis of these pheromone compounds.     

A Garratt-Braverman route to isoindolines and phthalans

Garratt-Braverman (GB) cyclization, two CC bond forming reaction in a single step, has been utilized to construct several isoindoline and phthalan derivatives. The precursors were the bispropargyl protected amines and ethers with one of the propargyl arm substituted with an alkene moiety. The GB cyclizations were generally carried out in presence of DBU in refluxing toluene. In case of the bispropargyl amine systems with the alkene arm substituted with electron withdrawing ester group, the cyclization occurred at room temperature. The yields of cyclization ranged from 64 to 86% which are acceptable considering the formation of two CC bonds. The protected isoindolines could be successfully deprotected by treatment with thiophenol in presence of triethyl amine and the corresponding free amines were isolated as the TFA salts.     

A facile one-pot stereoselective synthesis of trisubstituted (E)-2-methylalk-2-enoic acids from unactivated Baylis-Hillman adducts and a simple access to some important insect pheromones

An efficient one-pot stereoselective synthesis of trisubstituted (E)-2-methylalk-2-enoic acids has been accomplished by treatment of unactivated Baylis-Hillman adducts, 3-hydroxy-2-methylenealkanoates, with Al-NiCl₂·6H₂O in methanol at room temperature followed by hydrolysis. The method has been applied to the synthesis of three important insect pheromones, (4S,2E)-2,4-dimethyl-2-hexenoic acid, (+)-(S)-manicone and (+)-(S)-normanicone.     

Reaction of diaryl-1,2-diones with triphenylphosphine and diethyl azodicarboxylate leading to N,N-dicarboethoxy monohydrazones via a novel rearrangement

[reaction: see text]. A mechanistically novel reaction of diaryl-1,2-diones with diethyl azodicarboxylate and triphenylphosphine to afford N,N-dicarboethoxy monohydrazones is described. The reaction proceeds via a nitrogen to nitrogen migration of a carboethoxy group.     

Selective complexometric determination of mercury using sodium nitrite as masking agent

A complexo-titrimetric method for the determination of mercury(II) in the presence of other metal ions is described based on the selective masking ability of sodium nitrite. Mercury and other ions are initially complexed with an excess of EDTA and the surplus EDTA is titrated with Pb(NO₃)₂ solution at pH 5.0–6.0 using xylenol orange as indicator. An excess of solid NaNO₂ is then added to decompose the Hg(II)-EDTA complex and the released EDTA is titrated with standard Pb(NO₃)₂ solution. Accurate results were obtained for 10–65 mg of mercury with relative errors <0.3% and standard deviations < 0.03 mg. Sn(IV) and Pd(II) interfere but can be easily masked. The method is applied for the determination of Hg(II) in its alloy compositions and complexes.     

An efficient stereoselective synthesis of (E)- and (Z)-trisubstituted alkenes from unactivated Baylis-Hillman adducts using NaBH4/CuCl2·2H2O

A convenient and facile stereoselective synthesis of (E)- and (Z)-trisubstituted alkenes has been achieved by treatment of unactivated Baylis-Hillman adducts with NaBH₄ in the presence of CuCl₂·2H₂O at room temperature for 15 min.     

Semiconductor quantum dots and metal nanoparticles: syntheses,optical properties,and biological applications

We review the syntheses, optical properties, and biological applications of cadmium selenide (CdSe) and cadmium selenide–zinc sulfide (CdSe–ZnS) quantum dots (QDs) and gold (Au) and silver (Ag) nanoparticles (NPs). Specifically, we selected the syntheses of QDs and Au and Ag NPs in aqueous and organic phases, size- and shape-dependent photoluminescence (PL) of QDs and plasmon of metal NPs, and their bioimaging applications. The PL properties of QDs are discussed with reference to their band gap structure and various electronic transitions, relations of PL and photoactivated PL with surface defects, and blinking of single QDs. Optical properties of Ag and Au NPs are discussed with reference to their size- and shape-dependent surface plasmon bands, electron dynamics and relaxation, and surface-enhanced Raman scattering (SERS). The bioimaging applications are discussed with reference to in vitro and in vivo imaging of live cells, and in vivo imaging of cancers, tumor vasculature, and lymph nodes. Other aspects of the review are in vivo deep tissue imaging, multiphoton excitation, NIR fluorescence and SERS imaging, and toxic effects of NPs and their clearance from the body. Figure Semiconductor quantum dots and metal nanoparticles have extensive applications, e.g., in vitro and in vivo bioimaging Tamitake Itoh and Abdulaziz Anas contributed equally to this article.     

Reaction of Huisgen zwitterion with 1,2-benzoquinones and isatins: expeditious synthesis of dihydro-1,2,3-benzoxadiazoles and spirooxadiazolines

[reaction: see text] The zwitterionic intermediate generated from dialkyl azodicarboxylate and triphenylphosphine on reaction with 3-methoxy-1,2-benzoquinones afforded dihydro-1,2,3-benzoxadiazoles. N-Substituted isatins furnished spirooxadiazolines under similar conditions.     

One-pot, four-component reaction of isocyanides, dimethyl acetylenedicarboxylate, and cyclobutene-1,2-diones: a synthesis of novel spiroheterocycles

Isocyanides, dimethyl acetylenedicarboxylate, and cyclobutene-1,2-diones react in one-pot to afford novel spirocyclic compounds with double insertion of the isocyanide.