scholarly journals Mono- and disubstitutions of (hepta-2,5-diyne-1,7-diol) bis(dicobalt) derivatives — Selectivity in Nicholas reactions

2004 ◽  
Vol 82 (2) ◽  
pp. 366-374 ◽  
Author(s):  
Richard Guo ◽  
Romelo Gibe ◽  
James R Green
Keyword(s):  
Methyl Ether ◽  
Lewis Acids ◽  
Benzyl Ether ◽  
Nicholas Reaction ◽  
Benzyl Ethers ◽  
Alkyne Complexes ◽  
Derivatives Of ◽  
Alcohol Derivative ◽  
Ether Complex ◽  
Ether Alcohol

Bis(hexacarbonyldicobalt) complexes of benzyl ether – methyl ether or benzyl ether – acetate derivatives of hepta-2,5-diyne-1,7-diols undergo selective Lewis-acid-mediated Nicholas reactions with enol silanes, silyl ketene acetals, and allylstannanes, preferentially replacing the methyl ether or acetate function. Hydride nucleophiles are similarly incorporated selectively using a benzyl ether – alcohol derivative. Subsequent Nicholas reaction at the benzyloxy-bearing site may be accomplished with an identical or a different nucleophile, affording skipped 1,4-diyne-Co4(CO)12 complexes. In instances of lower selectivity for monosubstitution reactions with benzyl ethers, reverting to the use of a menthyl ether – methyl ether complex gives much improved selectivity for methyl ether substitution.Key words: cobalt alkyne complexes, Nicholas reaction, Lewis acids, 1,4-diynes.

Synthesis and Herbicidal Activity of Modified Monoterpenes Structurally Similar to Cinmethylin

Weed Science ◽  
1996 ◽  
Vol 44 (1) ◽  
pp. 7-11 ◽  
Author(s):  
Steven F. Vaughn ◽  
Gayland F. Spencer
Keyword(s):  
Petri Dish ◽  
Herbicidal Activity ◽  
Benzyl Ether ◽  
Weed Species ◽  
Test Species ◽  
Oxygenated Monoterpenes ◽  
Radicle Elongation ◽  
Benzyl Ethers ◽  
Germination And Growth ◽  
Derivatives Of

The preemergence herbicide cinmethylin is a benzyl ether derivative of the monoterpene 1,4-cineole. Other oxygenated monoterpenes (carvone, citronellol, fenchone, geraniol, and pulegone) were previously found to inhibit the germination and growth of several weed species while exhibiting low phytotoxicity to soybean. Benzyl ether derivatives of these oxygenated monoterpenes were synthesized and examined for preemergence and postemergence activity towards corn, soybean, wheat, and velvetleaf. Benzyl pulegyl ether exhibited the most preemergence activity when applied directly to the soil, completely inhibiting wheat and velvetleaf emergence at 1.0 kg ha−1while reducing soybean emergence 80%. Several of the benzyl ethers were more inhibitory to velvetleaf radicle elongation relative to cinmethylin but less inhibitory to corn and wheat radicle elongation in petri dish bioassays. Several of the benzyl ethers exhibited limited postemergence activity when applied at 1.0 kg ha−1to seedlings of the test species 10 d after emergence. The benzyl ether derivatives demonstrated altered selectivity and sensitivity as compared to the parent compounds and cinmethylin.

Visible Light-Mediated Oxidative Debenzylation

2020 ◽  
Author(s):  
Cristian Cavedon ◽  
Eric T. Sletten ◽  
Amiera Madani ◽  
Olaf Niemeyer ◽  
Peter H. Seeberger ◽  
...  
Keyword(s):  
Reaction Time ◽  
Visible Light ◽  
Functional Groups ◽  
Continuous Flow ◽  
Protecting Groups ◽  
Benzyl Ether ◽  
Complex Molecules ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Harsh Conditions

Protecting groups are key in the synthesis of complex molecules such as carbohydrates to distinguish functional groups of similar reactivity. The harsh conditions required to cleave stable benzyl ether protective groups are not compatible with many other protective and functional groups. The mild, visible light-mediated debenzylation disclosed here renders benzyl ethers orthogonal protective groups. Key to success is the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as stoichiometric or catalytic photooxidant such that benzyl ethers can be cleaved in the presence of azides, alkenes, and alkynes. The reaction time for this transformation can be reduced from hours to minutes in continuous flow. <br>

A versatile iodo(iii)etherification of terminal ethynylsilanes using BF3–OiPr2 and alkyl benzyl ethers

2021 ◽  
Author(s):  
Takuya Matsumoto ◽  
Hiroshi Hagiyama ◽  
Kanetsugu Kuribayashi ◽  
Kazuhito Hioki ◽  
Hikaru Fujita ◽  
...  
Keyword(s):  
Benzyl Ether ◽  
Alkoxyl Group ◽  
Group Transfer ◽  
Benzyl Ethers

BF3–OiPr2 and alkyl benzyl ether combining system enables a chemoselective alkoxyl group transfer in the synthesis of (E)-α-silyl-β-alkoxyvinyl-λ3-iodanes.

A Synthetic Route to Epoxyalkyl β-Laminaribiosides, Especially Suitable for Radiolabeling

1994 ◽  
Vol 47 (9) ◽  
pp. 1805 ◽  
Author(s):  
WM Best ◽  
RV Stick ◽  
DMG Tilbrook
Keyword(s):  
Synthetic Route ◽  
Benzyl Ethers ◽  
Derivatives Of

The major products in the controlled benzylation (NaH/PhCH2Cl) of allyl and but-3-enyl β-D-glucopyranosides were the 2,4,6-tri-O-benzyl ethers. Subsequent glycosidations of these tribenzyl ethers gave derivatives of allyl and but-3-enyl β- laminaribioside, the latter being subsequently transformed into 3,4-epoxybutyl β- laminaribioside.

An examination of VANOL, VAPOL, and VAPOL derivatives as ligands for asymmetric catalytic Diels–Alder reactions

2006 ◽  
Vol 84 (10) ◽  
pp. 1487-1503 ◽  
Author(s):  
Douglas P Heller ◽  
Daniel R Goldberg ◽  
Hongqiao Wu ◽  
William D Wulff
Keyword(s):  
Asymmetric Catalysis ◽  
Methyl Acrylate ◽  
Lewis Acids ◽  
Alder Reaction ◽  
Diels Alder ◽  
Asymmetric Catalytic ◽  
Diels Alder Reaction ◽  
Positive Cooperativity ◽  
Derivatives Of ◽  
Methyl Phenyl

Several derivatives of the vaulted biaryl ligand VAPOL were prepared and evaluated as chiral ligands for aluminum Lewis acids in the catalytic asymmetric Diels–Alder reactions of methyl acrylate and methacrolein with cyclopentadiene. The substituents on VAPOL were introduced into the 6- and 6′-positions in an effort to further extend the chiral pocket of the major groove, which contains the phenol functions at the 4- and 4′-positions. The set of four new ligands that have been prepared have the following groups introduced into the 6- and 6′-positions of VAPOL: bromide, methyl, phenyl and 3,5-di-t-butylphenyl. All of these ligands give lower asymmetric inductions than the unsubstituted VAPOL for the Diels–Alder reactions of both methyl acrylate and methacrolein. The positive cooperativity of added carbonyl compounds on the autoinduction in the Diels–Alder reaction of methyl acrylate and cyclopentadiene were also investigated with the VANOL and VAPOL ligands as well as the 6,6′-dibromo and 6,6′-diphenyl derivatives of VAPOL. Only the reaction with VAPOL showed any significant positive cooperativity. The reaction with VANOL was sluggish at –78 °C, but at higher temperatures, the reaction did exhibit positive cooperativity that was similar to that of VAPOL. Finally, no positive cooperativity was observed with the VAPOL ligand for the reaction of methacrolein and cyclopentadiene.Key words: Diels–Alder, asymmetric catalysis, vaulted biaryl ligands, VANOL, VAPOL.

Synthesis of methyl ether derivatives of sucrose

1975 ◽  
Vol 43 (2) ◽  
pp. 360-365 ◽  
Author(s):  
Michael G. Lindley ◽  
Gordon G. Birch ◽  
Riaz Khan
Keyword(s):  
Methyl Ether ◽  
Derivatives Of
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