Highly stereoselective formal

[formula: see text] Highly stereoselective formal [3 + 3] cycloaddition reactions of chiral vinylogous amides with alpha, beta-unsaturated iminiums are described. A mechanistic model is proposed to rationalize the observed stereoselectivity. The 6 pi-electron electrocyclic ring closure appears to be reversible, and a preferred rotation of the alkenyl group, one of the three 2 pi-components, during the ring closure step provides the thermodynamically favored diastereomer as the major product.     

Highly unsaturated polymers

Conclusions A means of synthesizing soluble polyacetylenic polymers of the diphenylmethane series was discovered.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 900–904, April, 1967.     

Highly Charged Aerosols

Colloid Journal - Previously discovered properties of an ensemble of highly charged droplets obtained by electrostatic dispersing of liquids have been discussed. It has been shown that the...     

Highly fluorinated benzobisbenzothiophenes

Expedient, facile syntheses of highly fluorinated benzobisbenzothiophenes (BBBT) are reported. Defined peripheral arrangements of sulfur and fluorine atoms lead to extensive crystalline networks of edge-to-edge S-F close contacts. The effects of various substitution patterns on self-assembly and electronic properties are described.     

Highly unsaturated polymers

Summary Bis-p-ethynylphenylmethane and 4,4-diethynylbibenzyl were synthesized and their oxidative polycondensation was carried out with formation of oligomers containing diacetylene units in their chains.     

Highly stereoselective benzylation of N-sulfinylketimines

The benzylation of N-sulfinyl ketimines with 2-(p-tolylsulfinyl)ethylbenzene and LDA afford t-alkylamines in good yields. The configuration at each one of the new chiral centers simultaneously created in this reaction is controlled by the configuration of the sulfinyl groups at the nucleophile and electrophile, respectively. Thus, the reactions of the (S)-sulfoxide 6 with the N-(S)-sulfinylketimines 3 only yield the anti diastereoisomers 18, whereas the syn diastereoisomers 19 are exclusively formed in reactions of (S)-6 with N-(R)-sulfinylketimines 3. After a two-step desulfinylation process ((i) TFA, (ii) Ra-Ni), this reaction provides a procedure for synthesizing any epimer of alpha,alpha-dibranched beta-alkylarylamines in optically pure form by choosing the configuration of the starting materials. A similar behavior is observed for carbanions derived from the O-protected 2-(p-tolylsulfinyl) benzyl alcohol 7 thus allowing the synthesis of the optically pure anti- and syn-1,2-amino alcohols containing a chiral quaternary carbon adjacent to the nitrogen.     

Highly efficient synthesis of ketoheptoses

A reliable, facile, high overall yielding and diastereoselective synthesis of ketoheptoses was developed and applied for preparation of the two most diabetogenic ketoheptoses as well as in a modified version for the synthesis of kamusol.     

Highly efficient glucosylation of flavonoids

Abstract  

A highly efficient procedure for glucosylation of flavonoids by acetobromoglucose is described. Glucosylation is carried out in a two-phase system CHCl₃/H₂O over 96 h using tetrabutylammonium bromide as phase-transfer catalyst. A purification procedure can be performed without column chromatography, and the yields of the glucosylated flavonoids are mostly quantitative. Acetylated glucosides were deprotected with sodium methanolate to afford the desired glucosides of flavonoids.     

Highly diastereoselective synthesis of anti-gamma-N-benzylamino-beta-hydroxyphosphonates

The reduction of gamma-N-benzylamino-beta-ketophosphonates derived from readily available amino acids can be carried out stereoselectively with Zn(BH(4))(2) at -78 degrees C to produce the anti-gamma-amino-beta-hydroxyphosphonates.     

Highly efficient synthesis of trimethylarsine

A convenient, highly efficient, and environmentally safe procedure for the preparation of trimethylarsine was proposed. A quantitative yield of this compound in the reaction of As₂O₃ with AIMe₃ was attained for the first time by using mechanochemical activation of the process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2122–2123, August, 1996.     

Highly chemoselective hydrogenolysis of iodoarenes

The catalytic hydrodehalogenation reaction using molecular hydrogen and Pd/C has been revisited. It is shown that the speed of removal of halogen increases with increasing electronegativity I < Br < Cl. Nevertheless, selective dehydrohalogenation in compounds containing other reducible functions can be achieved only with iodine and not with bromine or chlorine. Selective deiodination of iodobenzophenone could be accomplished without reducing the carbonyl group. Hydrogenolysis of azidoiodoaromatic compounds to the corresponding azido compounds is high yielding. This selectivity was exploited for the labeling of benzophenone- and azido-containing compounds by deuterium and tritium.     

Synthesis of Highly Substituted Hexahelicenes

C₂‐Symmetric hexahelicenes 3a – 3g , which bear four or six alkoxy chains, were prepared in eight‐to‐nine reaction steps in high overall yields. The final step consisted of a twofold oxidative photocyclization of the corresponding 2,7‐bis(2‐phenylethenyl)naphthalenes. Long (and branched) chains provide a good solubility and processability, which is a prerequisite for applications in organic synthesis and materials science.     

酰胺类化合物的高效合成研究

酰胺类化合物是有机化学中最常见的化合物之一, 在药物化学、生物化学以及高分子合成等领域都有着重要的应用. 近年来高效合成酰胺类化合物已经成为一个研究热点, 具有重要的意义.本文主要从过渡金属催化、有机小分子催化等方面讨论近几年来酰胺类化合物的合成研究进展, 并对其发展趋势进行展望.