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Computed Tomography (CT) Imaging is a widely used technique for medical and industrial applications. Iterative reconstruction algorithms are desired for improved reconstructed image quality and lower dose, but its computational requirements limit its practical usage. Reconstruction toolkit (RTK) is a package of open source GPU accelerated algorithms for CBCT (cone beam computed tomography). GPU based iterative algorithms gives immense acceleration, but it may not be optimized to use the GPU resources efficiently. Nvidia has released several profilers (Nsight-systems, Nsight-compute) to analyze the GPU implementation of an algorithm from compute utilization and memory efficiency perspective. This paper profiles and analyzes the GPU implementation of iterative FDK algorithm in RTK and optimizes it for computation and memory usage on a Quadro GV100 GPU with 32 GB of memory and over 5000 cuda cores. RTK based GPU accelerated iterative FDK when applied on a 4 byte per pixel input projection dataset of size 1.1 GB (512×512×1024) for 20 iterations, to reconstruct a volume of size 440 MB (512×512×441) with 4 byte per pixel, resulted in total runtime of ~11.2 seconds per iteration. Optimized RTK based iterative FDK presented in this paper took ~1.3 seconds per iteration.

An optically active N-heterocyclic carbene (NHC) has been metallated with [RhCl(COD)]2 to give a rhodium(I) monocarbene substituted complex. This complex has been fully characterized by 1H and 13C NMR spectroscopy and by single-crystal X-ray analysis. Preliminary tests of hydroformylation of styrene catalyzed with this compound have shown that branched to linear aldehyde ratio was rather low 0.67 (40%) and that the enantiomeric excess measured on the corresponding alcohols was only 10%. In the presence of an excess of triphenylphosphine, the ratio of branched to linear aldehyde increased markedly (91%) whereas the enantioselectivity of the reaction remained almost unchanged (12.5%).

A series of 1,6-dienes is cyclized to cyclopentene derivatives under neutral conditions with palladium chloride in ethanol or with in situ generated LPd2+ in acetonitrile.

The enantiomeric purity of a chiral compound is determined by NMR spectroscopic analysis of the diastereomers formed with a chiral derivatizing agent. Fluorinated O-aryllactic acids (FAC) 1 are efficient chiral reporters, whose spectacular remote anisotropic effects allow an easy identification and measurement of diastereomers. The remote effects are attributed to the particular design of FAC esters relative to other CDAs.

Many palladium-catalyzed organic reactions with tailored ligands, besides the princess of asymmetric catalysis, allylic alkylation, are suitable for enantioselective organic synthesis. This is clearly illustrated by the large number of promising examples such as the Heck reaction, and Wacker-type oxidations, cycloadditions, cycloisomerizations, carbonylations, and copolymerization of alkenes with carbon monoxide.

Chirality transfer from asymmetric ligands to the diene in ( η 4 - cis -1,2-divinylcyclohexane) rhodium complexes has been observed, leading to a slight excess of one of the two enantiomeric chair conformations of the cyclohexane ring. The importance of this phenomenon for the palladium-catalyzed oxidative cyclization of ( cis -1,22-divinylcyclohexane) using chiral carboxylates as nucleophiles is discussed.

The modification of the aromatic part of fluorinated O -aryl lactic acids allows the improvement of the fluorine NMR δΔ values in diastereomeric esters, but also the observation of other nuclei such as Hg ( δΔ > 6 ppm). The enantiomeric purity of chiral acids has been determined through the dl- and meso compounds formed from achiral diols.

Enantiomerically pure (1 S , 2 R )-epoxy indane and cis -(1 R , 2 S )-2-amino-1-indanol were synthesized via highly enantioselective lipase catalyzed transesterification of racemic trans -2-bromo-1-indanol.

A one-step synthesis of disubstituted brendane derivatives is described starting from (commercially) available vinyl norbornene by the Wacker-type oxidation with PdCl2/CuCl2 or PdCl2/CuCln/O2 (n=1,2). In addition to the formation of a new carbon carbon bond two different nucleophilic groups are incorporated with complete chemio-, regio- and high (>90%) stereoselectivity. The NMR and X-Ray structure analysis of a σ-π-palladium-bipyridine complex clearly establishes the stereochemistry of the prerogative intermediate and the position of the coordinated vinyl group in an ‘extracyclic’ position before the insertion-cyclisation step. This stereochemistry establishes the oxidative cleavage of the cyclised (cis-insertion) organopalladium intermediate to proceed with predominant (90%) inversion of configuration. A further ring opening reaction via Baeyer-Villiger oxidation has been developed showing the usefullness of the brendane derivatives for an easy access to functionalized quinane system(s) with complete stereocontrol of 5 stereogenic centers.

Reaction of the methyl ester of (−)-pinane-3-carboxylic acid 1 with the lithium derivative of 2-bromobut-2-ene affords, after dehydration, an isomeric mixture of 3-pinanyl cyclopentadienes 3 . Successive treatment with Li n Bu, Mo(CO) 6 and MeI gives rise to the title complex 5 , whose NMR spectra and X-ray structure unambiguously demonstrate the optical integrity and purity of this compound.

Diastereometric esters of O-arylated (R)-lactic acids have been studied by 1 H NMR spectroscopy with respect to their potential application as reagents for chiral analysis. The substitution pattern of the acid moiety of the ester was found to have a decisive influence on the magnitude of the resolution of the signals from the diastereoisomers

Nucleophilic attack of acetate ion on an olefinic bond of dichloro (η 4 -cis-1,2-divinylcyclohexane) palladium has been shown by NMR spectroscopy to lead to a σ,π-palladium (II) complex. This complex, which is also formed from nucleophilic attack on cis-1,2-divinylcyclohexane in the presence of palladium (II) acetate, spontaneously undergoes migratory insertion of the remaining olefinic bond into the palladium-carbon σ bond. This is followed by β-elimination to yield (1R*, 6S*, 7S*)-7-acetoxy-9-methylenebicyclo [4.3.0] nonane together with some rearranged products. The insertion has been shown to be favored by acidic reaction conditions

The Mukaiyama and Palomo reagents have been used for the kinetic resolution of racemic carboxylic acids or alcohols with homochiral alcohols or carboxylic acids, respectively, in the presence of triethylamine. Thus, enantiomerically enriched carboxylic acids (e.e.

Molecular sieves have been shown to improve greatly the stereoselectivity in the palladium(II)-catalyzed reaction of cis-1,2-divinylcyclohene with chiral acids. Reactions run with molecular sieves and derivatives of (R)-lactic acids as nucleophiles always yielded products with S configuration at the newly formed chiral center in contrast to reactions without molecular sieves that gave products with either S or R configuration at this chiral center. It appears that this effect has not been observed previously

The modification of the aromatic part of fluorinated O -aryl lactic acids allows the improvement of the fluorine NMR δΔ values in diastereomeric esters, but also the observation of other nuclei such as Hg ( δΔ > 6 ppm). The enantiomeric purity of chiral acids has been determined through the dl- and meso compounds formed from achiral diols.

Many palladium-catalyzed organic reactions with tailored ligands, besides the princess of asymmetric catalysis, allylic alkylation, are suitable for enantioselective organic synthesis. This is clearly illustrated by the large number of promising examples such as the Heck reaction, and Wacker-type oxidations, cycloadditions, cycloisomerizations, carbonylations, and copolymerization of alkenes with carbon monoxide.

Molecular sieves have been shown to improve greatly the stereoselectivity in the palladium(II)-catalyzed reaction of cis-1,2-divinylcyclohene with chiral acids. Reactions run with molecular sieves and derivatives of (R)-lactic acids as nucleophiles always yielded products with S configuration at the newly formed chiral center in contrast to reactions without molecular sieves that gave products with either S or R configuration at this chiral center. It appears that this effect has not been observed previously

The Mukaiyama and Palomo reagents have been used for the kinetic resolution of racemic carboxylic acids or alcohols with homochiral alcohols or carboxylic acids, respectively, in the presence of triethylamine. Thus, enantiomerically enriched carboxylic acids (e.e.

Nucleophilic attack of acetate ion on an olefinic bond of dichloro (η 4 -cis-1,2-divinylcyclohexane) palladium has been shown by NMR spectroscopy to lead to a σ,π-palladium (II) complex. This complex, which is also formed from nucleophilic attack on cis-1,2-divinylcyclohexane in the presence of palladium (II) acetate, spontaneously undergoes migratory insertion of the remaining olefinic bond into the palladium-carbon σ bond. This is followed by β-elimination to yield (1R*, 6S*, 7S*)-7-acetoxy-9-methylenebicyclo [4.3.0] nonane together with some rearranged products. The insertion has been shown to be favored by acidic reaction conditions

The mechanism of the loss of stereospecificity in palladium-catalyzed nucleophilic substitution of allylic substrates has been investigated. Eight substrates (cis and trans isomers of 1a-d) and two nucleophiles (Et2NH and NaCH(SO2Ph)2) were studied. In the animation reactions two pathways are responsible for the formation of anomalous inversion product, viz., isomerization of the starting material (path B, Scheme 2) and isomerization of the π-allyl intermediate via displacement of palladium by Pd(0) (path C, Scheme 2), the latter of which predominates. In the alkylation the results indicate that loss of stereospecificity is caused only by path C. The use of a more reactive substrate increased the stereospecificity of the reaction and suppressed the isomerization pathway. An analysis of the kinetics is consistent with the hypothesis that path C is the major pathway for the stereochemical loss.

A summary of the possible electron-transfer reactions between anthracene and the nitrosonium ion, and a convenient and simple method for the synthesis of 9,10-anthraquinone from anthracene, NaNO 2 and CH 3 OH in CH 2 Cl 2 /CF 3 COOH are presented. The suggestion that the formation of 9,10-anthraquinone in the N 2 O 4 nitration of anthracene originates from trapping of the anthracene radical cation by water is demonstrated to be invalid, e.g., by experiments involving H 2 18 O. Instead, 9,10-anthraquinone is suggested to be formed in the N 2 O 4 -based and in other related systems via follow-up reactions to an initial 1,4-addition across the 9,10 positions of anthracene

Racemic carboxylic acids have been kinetically resolved by means of homochiral alcohols using the DCC-esterification methodology. The best results were obtained with commercially available homochiral 1-(4-pyridyl)ethanol

This review deals with the application of Lewis super acids such as Al(III), In(III), and Sn(IV) triflates and triflimidates as catalysts in the synthesis of fragrance materials. Novel catalytic reactions involving C-C and C-heteroatom bond-forming reactions, as well as cycloisomerization processes are presented. In particular, Sn(IV) and Al(III) triflates were employed as catalysts in the selective cyclization of unsaturated alcohols to cyclic ethers, as well as in the cyclization of unsaturated carboxylic acids to lactones. The addition of thiols and thioacids to non-activated olefins, both in intra- and intermolecular versions, was efficiently catalyzed by In(III) derivatives. Sn(IV) Triflimidates catalyzed the cycloisomerization of highly substituted 1,6-dienes to gem-dimethyl-substituted cyclohexanes bearing an isopropylidene substituent. The hydroformylation of these unsaturated substrates, catalyzed by a Rh(I) complex with a bulky phosphite ligand, selectively afforded the corresponding linear aldehydes. The olfactory evaluation of selected heterocycles, carbocycles, and aldehydes synthesized is also discussed.

This review deals with the application of Lewis super acids such as Al(III), In(III), and Sn(IV) triflates and triflimidates as catalysts in the synthesis of fragrance materials. Novel catalytic reactions involving C-C and C-heteroatom bond-forming reactions, as well as cycloisomerization processes are presented. In particular, Sn(IV) and Al(III) triflates were employed as catalysts in the selective cyclization of unsaturated alcohols to cyclic ethers, as well as in the cyclization of unsaturated carboxylic acids to lactones. The addition of thiols and thioacids to non-activated olefins, both in intra- and intermolecular versions, was efficiently catalyzed by In(III) derivatives. Sn(IV) Triflimidates catalyzed the cycloisomerization of highly substituted 1,6-dienes to gem-dimethyl-substituted cyclohexanes bearing an isopropylidene substituent. The hydroformylation of these unsaturated substrates, catalyzed by a Rh(I) complex with a bulky phosphite ligand, selectively afforded the corresponding linear aldehydes. The olfactory evaluation of selected heterocycles, carbocycles, and aldehydes synthesized is also discussed.

The scope and limitations of palladium-catalyzed allylic acetoxylation of alkenes has been investigated, using benzoquinone-manganese dioxide as the reoxidation system. Unsubstituted cycloalkenes gave good to excellent yields of allylic acetates. Total yields were also good for many substituted cycloalkenes and for linear alkenes, but these substrates generally gave several isomeric acetates. The exploratory mechanistic studies show that the acetoxylation can proceed via both 1,2-acetoxypalladation and η 3 -allylpalladium complex formation. The keen balance between these processes depends on the structure of the alkene

The DCC-esterification method has been used to kinetically resolve racemic mixtures of alcohols. With simple chiral car☐ylic acids, such asO-aryl lactic acids, in the presence of various basic catalysts, mixtures of the enantiomerically enriched alcohols (e.e.

In non-racemic (1R,2R)-(1,2-dialkyl)-1,2-diaminocyclohexane palladium dichloride complexes the C2 symmetry of the diamine ligand is broken, resulting in selective R,S-coordination.

Bases such as caesium carbonate efficiently catalyze the regioselective ring opening of propylene and styrene oxide with various substituted pyrazoles.

Allylic acetoxylation of cycloalkenes: 2-cyclohepten-1-yl acetate product: 2-cyclohepten-1-yl acetate Keywords: metal-catalyzed reactions, palladium; replacement reactions, halogen by oxygen; N,N-dimethylformamide