Stereoselective Synthesis of (Z)-Allyl Alcohols through Coinage-Metal-Catalyzed Nucleophilic Addition of Benzo[d]isoxazoles with Unactivated Propargyl Alcohols

Synlett ◽  
2019 ◽  
Vol 30 (11) ◽  
pp. 1339-1345
Author(s):  
Zhiyuan Chen ◽  
Wenjin Wu ◽  
Tiantian Zheng ◽  
Jie Tan ◽  
Shouzhi Pu
Keyword(s):  
Stereoselective Synthesis ◽  
Silver Salt ◽  
Gold Catalyst ◽  
Building Blocks ◽  
Coinage Metal ◽  
Stereoselective Addition ◽  
Allyl Alcohols ◽  
Metal Catalyzed ◽  
Propargyl Alcohols

The Au/Ag-cocatalyzed stereoselective addition reaction of cyanophenol anion species generated in situ with unactivated propargyl alcohols to produce functionalized (Z)-allyl alcohols in mostly good yields is reported. Benzo[d]isoxazoles were found to be excellent building blocks for the production of highly reactive cyanophenol anions from Kemp elimination reactions, thus serving as a masked benzonitrile source for the preparation of organonitrile derivatives. Silver salt combined with gold catalyst were found to be necessary for the success of this transformation.

Alkylation Reactions with Alkylsulfonium Salts

Synthesis ◽  
2021 ◽  
Author(s):  
Ze-Yu Tian ◽  
Yu Ma ◽  
Cheng-Pan Zhang
Keyword(s):  
Organic Molecules ◽  
High Efficiency ◽  
Building Blocks ◽  
Organometallic Reagents ◽  
The Past ◽  
Wide Range ◽  
Catalyzed Reactions ◽  
Metal Catalyzed ◽  
Alkylation Reactions

Application of alkylsulfonium salts as alkyl transfer reagents in organic synthesis has reemerged over the past years. Numerous heteroatom- and carbon-centered nucleophiles, alkenes, arenes, alkynes, organometallic reagents, and others were readily alkylated by alkylsulfonium salts under mild conditions. The reactions feature convenience, high efficiency, readily accessible and structurally diversified alkylation reagents, good functional group tolerance, and a wide range of substrate types, allowing for facile synthesis of various useful organic molecules from the commercially available building blocks. This review summarizes the alkylation reactions using either isolated or in situ formed alkylsulfonium salts via nucleophilic substitution, transition-metal-catalyzed reactions, and photoredox processes.

scholarly journals Arenophile-Mediated Photochemical Dearomatization of Nonactivated Arenes

2020 ◽  
Vol 74 (7) ◽  
pp. 577-583 ◽  
Author(s):  
Mikiko Okumura ◽  
David Sarlah
Keyword(s):  
Natural Products ◽  
Transition Metal ◽  
Visible Light ◽  
Bioactive Compounds ◽  
Aromatic Compounds ◽  
Ring Opening ◽  
Organic Molecules ◽  
Building Blocks ◽  
Metal Catalyzed

Aromatic compounds are one of the most abundant classes of organic molecules and find utility as precursors for alicyclic hydrocarbon building blocks. While many established dearomatization reactions are exceptionally powerful, dearomatization with concurrent introduction of functionality, i.e. dearomative functionalization, is still a largely underdeveloped field. This review aims to provide an overview of our recent efforts and progress in the development of dearomative functionalization of simple and nonactivated arenes using arenophile-arene cycloaddition platform. These cycloadducts, formed via a visible-light-mediated [4+2]-photocycloaddition, can be elaborated in situ through olefin chemistry or transition-metal-catalyzed ring-opening with carbon-, nitrogen-, and oxygen-based nucleophiles, providing access to diverse structures with functional and stereochemical complexity. Moreover, the dearomatized products are amenable to further elaborations, which effectively install other functionalities onto the resulting alicyclic carbocycles. The utility of the arenophile-mediated dearomatization methods are also highlighted by the facile syntheses of natural products and bioactive compounds through novel disconnections.

Computational study on the mechanism of transition metal-catalyzed formation of highly substituted furo [3,4-d] [1,2] oxazines

2018 ◽  
Vol 17 (01) ◽  
pp. 1850011 ◽  
Author(s):  
Abigail Owusuwaa Gyamfi ◽  
Martin Amponsah Yeboah ◽  
Richard Tia ◽  
Evans Adei
Keyword(s):  
Intramolecular Cyclization ◽  
Activation Barrier ◽  
Computational Study ◽  
Gold Catalyst ◽  
Building Blocks ◽  
Rare Metal ◽  
Biologically Active ◽  
Gold Complex ◽  
Activation Barriers ◽  
Metal Catalyzed

The mechanism of gold(III)-catalyzed 1,3-dipolar [[Formula: see text]] cycloaddition reactions of 2-(1-alkynyl)-2-alken-1-ones with nitrones to afford highly-substituted furo [3,4-d] [1,2] oxazines, which are useful as structural skeletons in biologically active compounds and as synthetic building blocks in organic synthesis, have been studied computationally. The results show that the reaction proceeds via the formation of a [Formula: see text]-complex in which the gold moiety coordinates to the triple bond of the 2-(1-alkynyl)-2-alken-1-ones, resulting in an intramolecular cyclization of the gold intermediate to generate a carbocation intermediate which is trapped by the nucleophilic oxygen of the nitrone to form a furanyl–gold complex, which upon subsequent cyclization affords the furo [3,4-d] [1,2] oxazine as well as regenerates the gold catalyst. The highest activation barrier in the entire cycle is 19.5[Formula: see text]kcal/mol which accompanies the intramolecular cyclization step. The activation barriers for the reactions of 2-(1-alkynyl)2-alken-1-ones with electron-donating and cyclic substituents are generally lower compared to those of the parent 2-(1-alkynyl)2-alken-1-one while the reactions of 2-(1-alkynyl)2-alken-1-ones with electron-withdrawing substituents have higher activation barriers. Preliminary exploratory calculations on the possibility of replacing gold, an expensive and rare metal, with a copper-based catalyst for the reaction, show that for the key elementary steps, the Cu (III) catalyst is at least as active as the Au (III) complex, thus providing a cheaper route to furo [3,4-d] [1,2] oxazine.

scholarly journals A Dual CuH- and Pd-Catalyzed Stereoselective Synthesis of Highly Substituted 1,3-Dienes

2021 ◽  
Author(s):  
Chuan-Jin Hou ◽  
Alexander Schuppe ◽  
James Levi Knippel ◽  
Anton Ni ◽  
Stephen Buchwald
Keyword(s):  
Stereoselective Synthesis ◽  
Building Blocks ◽  
Conjugated Dienes ◽  
Synthetic Chemistry

Conjugated dienes are versatile building blocks and prevalent substructures in synthetic chemistry. Herein, we report a method for the stereoselective hydroalkenylation of alkynes, utilizing readily available enol triflates. We leveraged an in situ generated and geometrically pure vinyl-Cu(I) species to form the Z,Z- or Z,E-1,3-dienes in excellent stereoselectivity and yield. This approach allowed for the synthesis of highly substituted Z-dienes, including pentasubstituted 1,3-dienes, which are difficult to prepare by existing approaches.

Laboratory and in-situ analysis of comet dust

1988 ◽  
Vol 46 ◽  
pp. 8-9
Author(s):  
D.E. Brownlee ◽  
A.L. Albee
Keyword(s):  
Electron Microscopy ◽  
Solar System ◽  
Laboratory Study ◽  
Isotopic Analysis ◽  
Building Blocks ◽  
Sem Analysis ◽  
Early Solar System ◽  
Cometary Material ◽  
Comet Dust

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.

scholarly journals Exploring Cu/Al cluster growth and reactivity: from embryonic building blocks to intermetalloid, open-shell superatoms

2021 ◽  
Author(s):  
Max Schütz ◽  
Christian Gemel ◽  
Maximilian Muhr ◽  
Christian Jandl ◽  
Samia Kahlal ◽  
...  
Keyword(s):  
Closed Shell ◽  
Building Blocks ◽  
Open Shell ◽  
Cluster Growth ◽  
Powerful Technique

Cu/Al cluster growth reactions leading to open- and closed-shell superatoms are investigated. Therein, LIFDI-MS is presented as a powerful technique for the in situ detection of cluster identities and reactivity patterns.

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