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Benzylic tertiary alcohols

Titouan Royal, Yann Baumgartner, Olivier Baudoin
A general and highly enantioselective arylation of carbamates derived from primary alcohols was developed by combining Hoppe's sparteine-mediated asymmetric lithiation with Negishi cross-coupling. Coupled with Aggarwal's lithiation-borylation sequence, the current method provides a short and divergent access to a variety of enantioenriched secondary and tertiary benzylic alcohols.
December 20, 2016: Organic Letters
Njomza Ajvazi, Stojan Stavber
The efficiency of direct conversion of tertiary alcohols bearing a β-hydrogen atom to vicinal halohydrins-chlorohydrins and bromohydrins-under green reaction conditions was tested preliminarily on model tertiary benzyl alcohols. Tertiary alcohols were successfully directly halogenated to vicinal halohydrins with N-halosuccinimide in aqueous media. The efficiency of the reaction in water was significantly improved in the presence of sodium dodecyl sulphate as the surfactant.
October 2, 2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Bao-Sheng Li, Yuhuang Wang, Rupert S J Proctor, Yuexia Zhang, Richard D Webster, Song Yang, Baoan Song, Yonggui Robin Chi
Benzyl bromides and related molecules are among the most common substrates in organic synthesis. They are typically used as electrophiles in nucleophilic substitution reactions. These molecules can also be activated via single-electron-transfer (SET) process for radical reactions. Representative recent progress includes α-carbon benzylation of ketones and aldehydes via photoredox catalysis. Here we disclose the generation of (nitro)benzyl radicals via N-heterocyclic carbene (NHC) catalysis under reductive conditions...
2016: Nature Communications
Qi Zhou, Kelsey M Cobb, Tianyu Tan, Mary P Watson
Asymmetric preparation of all-carbon quaternary stereocenters is an important goal. Despite advances in formation of highly enantioenriched products with quaternary stereocenters proximal to a functional group, methods to install quaternary stereocenters isolated from functional groups are limited. Transition metal catalysis offers a potential solution, but prior cross couplings are limited to allylic substrates or deliver little to no enantiomeric enrichment. We report a stereospecific, nickel-catalyzed Suzuki-Miyaura arylation of tertiary benzylic acetates to deliver products with diaryl and triaryl quaternary stereocenters in high yields and ee's...
September 21, 2016: Journal of the American Chemical Society
Erik Lindstedt, Elin Stridfeldt, Berit Olofsson
An efficient and transition-metal-free method is presented to access tertiary alkyl aryl ethers by arylation of tertiary alcohols with ortho-substituted diaryliodonium salts. The scope covers cyclic and acyclic aliphatic, benzylic, allylic, and propargylic tertiary alcohols as well as primary and secondary fluorinated alcohols. The methodology gives access to alkyl aryl ethers of previously unprecedented steric congestion. Furthermore, the versatility of the developed procedure was demonstrated by arylation of the pro-drug mestranol...
September 2, 2016: Organic Letters
Erik Lindstedt, Elin Stridfeldt, Berit Olofsson
An efficient and transition-metal-free method is presented to access tertiary alkyl aryl ethers by arylation of tertiary alcohols with ortho-substituted diaryliodonium salts. The scope covers cyclic and acyclic aliphatic, benzylic, allylic, and propargylic tertiary alcohols as well as primary and secondary fluorinated alcohols. The methodology gives access to alkyl aryl ethers of previously unprecedented steric congestion. Furthermore, the versatility of the developed procedure was demonstrated by arylation of the pro-drug mestranol...
August 16, 2016: Organic Letters
Susan L Zultanski, Jingyi Zhao, Shannon S Stahl
A modular Cu/ABNO catalyst system has been identified that enables efficient aerobic oxidative coupling of alcohols and amines to amides. All four permutations of benzylic/aliphatic alcohols and primary/secondary amines are viable in this reaction, enabling broad access to secondary and tertiary amides. The reactions exhibit excellent functional group compatibility and are complete within 30 min-3 h at rt. All components of the catalyst system are commercially available.
May 25, 2016: Journal of the American Chemical Society
Brandon T Kelley, Jennifer C Walters, Sarah E Wengryniuk
A facile method for the synthesis of challenging medium-sized cyclic ethers has been developed via a novel oxidative rearrangement of benzylic tertiary alcohols. The reaction provides access to cyclic acetals with diverse substitution at both C2 and the aromatic ring. The unique reactivity is enabled by poly(cationic) hypervalent iodine reagents and represents the first synthetic application of this underexplored class of compounds.
April 15, 2016: Organic Letters
Barry M Trost, Michael C Ryan
Allylic chlorides prepared from commercially available trans-1,4-dichloro-2-butene were converted to trans-disubstituted 5- and 6-membered ring systems with perfect diastereoselectivity and high enantioselectivity under chiral ruthenium catalysis. These products contain stereodefined secondary and tertiary alcohols that originate from the trapping of an alkylruthenium intermediate with adventitious water. Key to the success of this transformation was the development of a new BINOL-based phosphoramidite ligand containing bulky substitution at its 3- and 3'-positions...
March 9, 2016: Journal of the American Chemical Society
Sampa Pal, Sanhita Maity, Subrata Sardar, Jishnu Chakraborty, Umesh Chandra Halder
Many proteins form ordered irreversible aggregates called amyloid fibrils which are responsible for several neurodegenerative diseases. β-lactoglobulin (β-lg), an important globular milk protein, self-assembles to form amyloid-like fibrils on heating at low pH. The present study investigated the effects of two commonly used organic solvents acetonitrile (MeCN) and antimicrobial preservative benzyl alcohol (BA) on the conformation and self-assembly of β-lg at ambient condition. Both MeCN and BA induced a concentration-dependent conformational change showing exposure of hydrophobic patches, loss of tertiary structure and higher α-helical structure at moderate concentrations...
March 2016: International Journal of Biological Macromolecules
Shehani N Mendis, Jon A Tunge
Enantioenriched benzyl esters of propiolic acids undergo highly stereospecific decarboxylative coupling to provide 1,1-diarylethynyl methanes. This sp-sp(3) coupling does not require strongly basic conditions or preformed organometallics and produces CO2 as the sole byproduct. Ultimately, this method results in the successful transfer of stereochemical information from secondary benzyl alcohols to generate enantioenriched tertiary diarylmethanes.
November 6, 2015: Organic Letters
Samuel J Thompson, Danny Q Thach, Guangbin Dong
Here, a palladium-catalyzed functionalization of unactivated sp(3) C-H bonds with internal alcohol nucleophiles is described. Directed by an oxime-masked alcohol, annulation chemoselectively occurs at the β position, leading to a range of aliphatic cyclic ethers with four- to seven-membered rings. Tethered primary, secondary, and tertiary free hydroxyl groups can all react to give the corresponding cyclized products. In addition, benzyl and silyl protected alcohols can also be directly coupled. An sp(3) C-H activation/intramolecular SN2 pathway was proposed...
September 16, 2015: Journal of the American Chemical Society
Sun Young Lee, Jung Wha Jung, Tae-Hyun Kim, Hee-Doo Kim
The first asymmetric synthesis of (R,R)-clemastine (1) has been accomplished by the coupling of (R)-tertiary alcohol 2 and (R)-chloroethylpyrrolidine 3 via O-alkylation. (R)-Tertiary alcohol 2 was synthesized by stereoselective alkylation of chiral α-benzyloxy ketone with Grignard reagent via chelation-controlled 1,4-asymmetric induction. In the reaction, chiral benzyl group acts as a chiral auxiliary as well as a protecting group. (R)-Chloroethylpyrrolidine 3 was prepared by asymmetric transformation starting with L-homoserine lactone, in which racemization-minimized N-allylation and ring-closing metathesis were involved as key steps...
December 2015: Archives of Pharmacal Research
Steven Bloom, Desta Doro Bume, Cody Ross Pitts, Thomas Lectka
To expand upon the recent pioneering reports of catalyzed sp(3) C-H fluorination methods, the next rational step is to focus on directing "radical-based fluorination" more effectively. One potential solution entails selective C-C bond activation as a prelude to selective fluorination. Herein, we report the tandem photocatalyzed ring-opening/fluorination reactions of cyclopropanols by 1,2,4,5-tetracyanobenzene (TCB) and Selectfluor to afford a process tantamount to site-selective β-fluorination of carbonyl-containing compounds...
May 26, 2015: Chemistry: a European Journal
Maria De Rosa, Johan Unge, Hitesh V Motwani, Åsa Rosenquist, Lotta Vrang, Hans Wallberg, Mats Larhed
Seven novel tertiary alcohol containing linear HIV-1 protease inhibitors (PIs), decorated at the para position of the benzyl group in the P1' side with (hetero)aromatic moieties, were synthesized and biologically evaluated. To study the inhibition and antiviral activity effect of P1-P3 macrocyclization, 14- and 15-membered macrocyclic PIs were prepared by ring-closing metathesis of the corresponding linear PIs. The macrocycles were more active than the linear precursors and compound 10f, with a 2-thiazolyl group in the P1' position, was the most potent PI of this new series (Ki 2...
August 14, 2014: Journal of Medicinal Chemistry
Yan Lou, Xiaochun Han, Andreas Kuglstatter, Rama K Kondru, Zachary K Sweeney, Michael Soth, Joel McIntosh, Renee Litman, Judy Suh, Buelent Kocer, Dana Davis, Jaehyeon Park, Sandra Frauchiger, Nolan Dewdney, Hasim Zecic, Joshua P Taygerly, Keshab Sarma, Junbae Hong, Ronald J Hill, Tobias Gabriel, David M Goldstein, Timothy D Owens
Structure-based drug design was used to guide the optimization of a series of selective BTK inhibitors as potential treatments for Rheumatoid arthritis. Highlights include the introduction of a benzyl alcohol group and a fluorine substitution, each of which resulted in over 10-fold increase in activity. Concurrent optimization of drug-like properties led to compound 1 (RN486) ( J. Pharmacol. Exp. Ther. 2012 , 341 , 90 ), which was selected for advanced preclinical characterization based on its favorable properties...
January 8, 2015: Journal of Medicinal Chemistry
Ryohei Kakuchi, Patrick Theato
A Mitsunobu reaction of trifluoroacetamide (TFA amide) and alcohols is used in a postpolymerization modification process. The reaction is conducted on polystyrene (PSt) bearing 20 mol% TFA amide groups with 4-methyl benzyl alcohol in the presence of a N,N,N′,N ′-tetramethylazodicarboxamide and tributylphosphine as mediators. The Mitsunobu reaction on polymer proceeds efficiently, as confirmed by the obvious precipitation generation during the reaction and the conversion of TFA amide moiety reached 88.6% confirmed by 19 F NMR measurement, yielding PSt bearing tertiary TFA amide moieties...
March 2014: Macromolecular Rapid Communications
Andrea Gualandi, Luca Mengozzi, Jessica Giacoboni, Steve Saulnier, Moira Ciardi, Pier Giorgio Cozzi
Recently, the direct substitution of allylic, benzylic, and tertiary alcohols has been achieved via SN 1-type reactions with catalytic amounts of Brønsted or Lewis acids. When a new stereogenic center is formed most of these transformations produce the desired product as a racemate, as these reactions proceed through carbenium ions. The arsenal of activation modes available in organocatalysis can be used to set up suitable reaction conditions in which chiral nucleophiles (enamine catalysis) or chiral electrophiles (iminium catalysis, chiral counterion catalysis) can easily be generated...
October 2014: Chirality
Lodi Mahendar, Gedu Satyanarayana
An efficient domino Pd-catalyzed transformation of simple ortho-bromobenzyl tertiary alcohols to chromenes is presented. Their formation is believed to proceed via the formation of a five-membered palladacycle, which, in turn, involves in an intermolecular homocoupling with the second ortho-bromobenzyltertiary alcohol to yield the homo-biaryl bond followed by intramolecular C-O bond formation. Interestingly, when there is an allylic substituent on the benzylic carbon atom, a chemoselective switch was observed, which preferred intramolecular Heck coupling and gave indenols...
March 7, 2014: Journal of Organic Chemistry
Yoshinari Sawama, Ryota Goto, Saori Nagata, Yuko Shishido, Yasunari Monguchi, Hironao Sajiki
Methyl and benzyl ethers are widely utilized as protected alcohols due to their chemical stability, such as the low reactivity of the methoxy and benzyloxy groups as leaving groups under nucleophilic conditions. We have established the direct azidation of chemically stable methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols. The present azidation chemoselectively proceeds at the secondary or tertiary benzylic positions of methyl benzyl ethers or unsymmetrical dibenzyl ethers and is also applicable to direct allylation, alkynylation, and cyanation reactions, as well as the azidation...
February 24, 2014: Chemistry: a European Journal
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