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Benzylic tertiary alcohols

Benjamin Ciszek, Ivana Fleischer
Herein we report the first homogeneous palladium-based transfer hydrogenolysis of benzylic alcohols using an in situ formed palladium-phosphine complex and formic acid as reducing agent. The reaction requires a catalyst loading as low as only 1 mol% of palladium and just a slight excess of reductant to obtain the deoxygenated alkylarenes in good to excellent yields. Besides demonstrating the broad applicability for primary, secondary and tertiary benzylic alcohols, a reaction intermediate could be identified...
April 12, 2018: Chemistry: a European Journal
Alexander S Burns, Christopher C Ross, Scott D Rychnovsky
Birman's HBTM catalyst is effective for the enantioselective acylation and kinetic resolution of benzylic secondary alcohols. The enantioselective acylation has now been extended to secondary alcohols bearing electron-withdrawing groups such as halides and other heteroatoms. The level of selectivity is modest to good and is sufficient for determining configuration using the competing enantioselective conversion method. A mathematical analysis identifies conditions for achieving maximum differences in conversion and, consequently, assigning configuration with greater confidence...
March 2, 2018: Journal of Organic Chemistry
Wenfang Wang, Daqian Xu, Qiangsheng Sun, Wei Sun
A tetradentate nitrogen ligand containing a benzimidazole ring and an electron-rich pyridine ring was developed, the resulting manganese complex exhibited good activity in the C-H oxidation of simple alkanes. In particular, cyclic aliphatic alkanes were transformed into ketones in very good yields (up to 89 %) by using environmentally benign H2 O2 as the terminal oxidant. This protocol was also applied successfully in benzylic C-H oxidation, giving the corresponding ketones with very good selectivities. In addition, tertiary C-H bond oxidation of complex molecules by the manganese complex showed potential utility for assembling alcohols with good selectivity in late-stage chemical synthesis...
February 9, 2018: Chemistry, An Asian Journal
Ricardo I Rodríguez, Elsie Ramírez, Francisco Yuste, Rubén Sánchez-Obregón, José Alemán
The generation of diastereomerically enriched secondary benzyl propargyl alcohols by the asymmetric addition of ortho-sulfinylbenzyl carbanions to sulfonylacetylene derivatives via formation of a Csp-Csp3 bond is described. This reaction proceeds through an unusual α-attack (anti-Michael addition) of the ortho-sulfinylbenzyl carbanions, followed by elimination of the arylsulfonyl moiety. The scope of this alkynylation reaction is also discussed. Moreover, the development of a new approach for the synthesis of optically active tertiary benzylpropargyl alcohols is described, discussing the possible stereocourse of the reaction so as the influence of the ether 18-crown-6 and steric importance of acetylenic substituent...
February 16, 2018: Journal of Organic Chemistry
Marjan Jereb, Dejan Vražič
Iodine-catalyzed transformations of alcohols under solvent-free reaction conditions (SFRC) and under highly concentrated reaction conditions (HCRC) in the presence of various solvents were studied in order to gain insight into the behavior of the reaction intermediates under these conditions. Dimerization, dehydration and substitution were the three types of transformations observed with benzylic alcohols. Dimerization and substitution reactions were predominant in the case of primary- and secondary alcohols, whereas dehydration prevailed in the case of tertiary alcohols...
December 2017: Acta Chimica Slovenica
Sajjad Rahimi, Farhad Panahi, Marzieh Bahmani, Nasser Iranpoor
The reaction of secondary and tertiary benzyl alcohols activated by 2,4,6-trichloro-1,3,5-triazine (TCT) with aldehydes in the presence of NiCl2 ·dmg as a precatalyst in ethylene glycol afforded ethers at room temperature. A selective C-O vs C-C bond formation was observed for the secondary and tertiary benzyl alcohols in comparison with primary ones.
January 19, 2018: Journal of Organic Chemistry
Rosemary A Croft, James J Mousseau, Chulho Choi, James A Bull
3-Sulfanyl-oxetanes are presented as promising novel bioisosteric replacements for thioesters or benzyl sulfides. From oxetan-3-ols, a mild and inexpensive Li catalyst enables chemoselective C-OH activation and thiol alkylation. Oxetane sulfides are formed from various thiols providing novel motifs in new chemical space and specifically as bioisosteres for thioesters due to their similar shape and electronic properties. Under the same conditions, various π-activated secondary and tertiary alcohols are also successful...
January 19, 2018: Chemistry: a European Journal
Yaqi Yang, Zihang Ye, Xu Zhang, Yipeng Zhou, Xiantao Ma, Hongen Cao, Huan Li, Lei Yu, Qing Xu
Alcohols can be efficiently converted into the useful thioethers by a transition metal- and base-free dehydrative S-alkylation reaction with thiols or disulfides by employing alkyl halides as the effective catalyst. This simple and efficient method is a green and practical way for the preparation of thioethers, as it tolerates a wide range of substrates such as aryl and alkyl thiols, as well as benzylic, allylic, secondary, tertiary, and even the less reactive aliphatic alcohols.
November 22, 2017: Organic & Biomolecular Chemistry
Hu Zhang, Stephen L Buchwald
We report a Pd-catalyzed stereospecific α-arylation of optically pure 2,3-epoxy-1,1,1-trifluoropropane (TFPO). This method allows for the direct and reliable preparation of optically pure 2-CF3-2-(hetero)aryloxiranes, which are precursors to many CF3-substituted tertiary alcohols. The use of continuous-flow methods has allowed the deprotonation of TFPO and subsequent zincation at higher temperature compared to that under traditional batch conditions.
August 10, 2017: Journal of the American Chemical Society
Syed R Huq, Shicheng Shi, Ray Diao, Michal Szostak
Samarium(II) iodide-water and samarium(II) iodide-water-amine complexes have been recognized as valuable reagents for the selective generation of aminoketyl radicals from amides and derivatives. The resulting aminoketyl radicals can undergo reduction or reductive cyclization pathways, providing a powerful method for (i) direct synthesis of alcohols from amides by the challenging N-C bond scission and (ii) synthesis of nitrogen-containing heterocycles via polarity reversal of the amide bond. This report describes mechanistic investigation into samarium(II) iodide-water and samarium(II) iodide-water-amine-mediated generation of benzylic aminoketyl radicals from aromatic primary, secondary, and tertiary amides (benzamides)...
June 22, 2017: Journal of Organic Chemistry
Yu-Feng Liang, Ning Jiao
The selective oxidation of organic molecules is a fundamentally important component of modern synthetic chemistry. In the past decades, direct oxidative C-H and C-C bond functionalization has proved to be one of the most efficient and straightforward methods to synthesize complex products from simple and readily available starting materials. Among these oxidative processes, the use of molecular oxygen as a green and sustainable oxidant has attracted considerable attention because of its highly atom-economical, abundant, and environmentally friendly characteristics...
June 21, 2017: Accounts of Chemical Research
Hai Huang, Jun Yong Kang
A novel protocol for extending the scope of the Mitsunobu reaction to include amine nucleophiles to form C-N bonds through the utilization of N-heterocyclic phosphine-butane (NHP-butane) has been developed. Both aliphatic alcohols and benzyl alcohols are suitable substrates for C-N bond construction. Various acidic nucleophiles such as benzoic acids, phenols, thiophenol, and secondary sulfonamide also provide the desired products of esters, ethers, thioether, and tertiary sulfonamide with 43-93% yields. Importantly, C-N bond-containing pharmaceuticals, Piribedil and Cinnarizine, have been synthesized in one step from the commercial amines under this Mitsunobu reaction system...
June 15, 2017: Journal of Organic Chemistry
Kim Spielmann, Renata Marcia de Figueiredo, Jean-Marc Campagne
A straightforward strategy for the syntheses of curcumene and ar-himachalene is reported. Synthetic highlights include a catalytic and asymmetric vinylogous Mukaiyama reaction and a stereospecific hydrogenolysis of a tertiary benzylic center using Pd/C or Ni/Raney catalysts. Notably, using Ni/Raney, the stereoselectivity outcome (inversion vs retention) of the hydrogenolysis depends on the tertiary benzylic alcohol substitution.
May 5, 2017: Journal of Organic Chemistry
Rosa Ortiz, Raquel P Herrera
With the increasing concern for sustainability, the use of environmentally friendly media to perform chemical processes has attracted the attention of many research groups. Among them, the use of water, as the unique solvent for reactions, is currently an active area of research. One process of particular interest is the direct nucleophilic substitution of an alcohol avoiding its preliminary transformation into a good leaving group, since one of the by-products in this approach would be water. The direct substitution of allylic, benzylic, and tertiary alcohols has been achieved through SN1-type reactions with catalytic amounts of Brønsted or Lewis acids; however, organic solvents are often required...
April 1, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
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
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