An Enantiospecific Formal Total Synthesis of the 5-8-5 Tricyclic Diterpene ent-Fusicoauritone

An enantiospecific formal total synthesis of the 5-8-5 tricyclic diterpene fusicoauritone has been accomplished, starting from 5-isopropyl-2-methylcyclopent-1-enemethanol [available in three steps from (R)-dihydrolimonene] employing two ring-closing-metathesis reactions for the construction of the eight- and five-membered rings.

Synthesis of 5-p-hydroxybenzyl-5,6-dihydro-2-naphthol, (+/-)-sequirin-d

A high-yield six-step synthesis of sequirin D (1a), a naturally occurring norlignan, is described. Michael addition of deoxyanisoin (2) to acrylonitrile gives a ketonitrile (3), which on Wolff–Kishner reduction is reduced and hyrolysed in situ to 4,5-bis-p-methoxyphenylpentanoic acid (4). Cyclodehydration of (4) with polyphosphoric acid, followed by borohydride reduction and dehydration furnishes di-O-methylsequirin D (1b) which affords on demethylation sequirin D (1a) in an overall yield from (2) of 60%. The key synthon (4) has also been prepared by three other routes.

C-H functionalization of tertiary amines by cross dehydrogenative coupling reactions: solvent-free synthesis of alpha-aminonitriles and beta-nitroamines under aerobic condition

A solvent-free synthesis of alpha-aminonitriles and beta-nitroamines by oxidative cross-dehydrogenative coupling under aerobic condition is reported. A catalytic amount of molybdenum(VI) acetylacetonoate was found to catalyze cyanation of tertiary amines to form alpha-aminonitriles, whereas vanadium pentoxide was found to promote aza-Henry reaction to furnish beta-nitroamines. Both of these environmentally benign reactions are performed in the absence of solvents using molecular oxygen as an oxidant.

Gas-phase synthesis of size-classified polyhedral In(2)O(3) nanoparticles

Monodisperse polyhedral In(2)O(3) nanoparticles were synthesized by differential mobility classification of a polydisperse aerosol formed by evaporation of indium at atmospheric pressure. When free molten indium particles oxidize, oxygen is absorbed preferentially on certain planes leading to the formation of polyhedral In(2)O(3) nanoparticles. It is shown that the position of oxygen addition, its concentration, the annealing temperature and the type of carrier gas are crucial for the resulting particle shape and crystalline quality. Semiconducting nanopolyhedrals, especially nanocubes used for sensors, are expected to offer enhanced sensitivity and improved response time due to the higher surface area as compared to spherical particles.

Selective synthesis of metallic and semiconducting single-walled carbon nanotubes

As-prepared single-walled carbon nanotubes (SWNTs) are generally mixtures of semiconducting and metallic species, the proportion of the former being around 67%. Since most applications of SWNTs are best served by semiconducting or metallic nanotubes, rather than by mixtures of the two, methods which would directly yield semiconducting and metallic SWNTs in pure form are desirable. In this article, we present the available methods for the direct synthesis of such SWNTs along with the methods available to separate semiconducting and metallic SWNTs from mixtures. We also discuss the synthesis of Y-junction carbon nanotubes.

Low temperature synthesis of layered NaxCoO2 and KxCoO2 from NaOH/KOH fluxes and their ion exchange properties

We report a low temperature synthesis of layered Na0×20CoO2 and K0×44CoO2 phases from NaOH and KOH fluxes at 400°C. These layered oxides are employed to prepare hexagonal HCoO2, LixCoO2 and Delafossite AgCoO2 phases by ion exchange method. The resulting oxides were characterised by powder X-ray diffraction, X-ray photoelectron spectroscopy, SEM and EDX analysis. Final compositions of all these oxides are obtained from chemical analysis of elements present. Na0×20CoO2 oxide exhibits insulating to metal like behaviour, whereas AgCoO2 is semiconducting.

Synthesis of configurable architectures for DSP algorithms

ASICs offer the best realization of DSP algorithms in terms of performance, but the cost is prohibitive, especially when the volumes involved are low. However, if the architecture synthesis trajectory for such algorithms is such that the target architecture can be identified as an interconnection of elementary parameterized computational structures, then it is possible to attain a close match, both in terms of performance and power with respect to an ASIC, for any algorithmic parameters of the given algorithm. Such an architecture is weakly programmable (configurable) and can be viewed as an application specific instruction-set processor (ASIP). In this work, we present a methodology to synthesize ASIPs for DSP algorithms.

Tractable theories for the synthesis of neural networks

The Radius of Direct attraction of a discrete neural network is a measure of stability of the network. it is known that Hopfield networks designed using Hebb's Rule have a radius of direct attraction of Omega(n/p) where n is the size of the input patterns and p is the number of them. This lower bound is tight if p is no larger than 4. We construct a family of such networks with radius of direct attraction Omega(n/root plog p), for any p greater than or equal to 5. The techniques used to prove the result led us to the first polynomial-time algorithm for designing a neural network with maximum radius of direct attraction around arbitrary input patterns. The optimal synaptic matrix is computed using the ellipsoid method of linear programming in conjunction with an efficient separation oracle. Restrictions of symmetry and non-negative diagonal entries in the synaptic matrix can be accommodated within this scheme.

Synthesis of free standing carbon nanosheet using electron cyclotron resonance plasma enhanced chemical vapor deposition

Carbon nanosheets (CNSs) have been synthesized by electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (PECVD) using a mixture of acetylene and argon gases on copper foil as the substrate. Micrometer-wide carbon sheets consisting of several atomic layers thick graphene sheets have been synthesized by controlled decomposition of carbon radicals in ECR-PECVD. Raman spectroscopy of these films revealed characteristics of a disordered graphitic sheet. Thick folded carbon-sheets and a semi transparent freestanding CNSs have been observed by scanning electron microscopy. This is a promising technique to synthesize free standing CNSs and can be used in the fabrication of nanoelecronic devices in future. (C) 2012 Elsevier B.V. All rights reserved.

Synthesis of 2-Deoxy-2-C-alkyl Glycal and Glycopyranosides from 2-Hydroxy Glycal Ester

A method to convert 2-hydroxy glycol ester to the corresponding corresponding 2-deoxy-2-C-alkyl glycol in a facile manner, through key reactions including (i) C-allylation at C-1, (ii) Wittig reaction, and (iii) Cope rearrangement of a 1,5-diene derivative, is reported. The alpha-anomer of the 1,5-diene derivative underwent Cope rearrangement to afford 2-deoxy-2-C-glycal derivative, whereas the beta-anomer was found to be unreactive. Employing this sequence, was transformed to 3,4,6-tri-O-benzyl-2-deoxy-2-C-alkyl-1,5-anhydro-D-arabino-hex-1-enitol. 2-Deoxy-2-C-alkyl glycol derivative is a suitable glycosyl donor to prepare 2-deoxy-2-C-alkyl glycosides, mediated through haloglycosylation and a subsequent dehalogenation. A number of 2-deoxy-2-C-alkyl glycosides, with both glycosyl and nonglycosyl moieties at the reducing end, are thus prepared from the glycol.