Chain elongation of primary alcohols of carbohydrates

The chain elongation of primary alcohol of saccharides (α-d-ribose, α-d-glucose, α-d-mannose) and a disaccharide (α-d-melibiose) has been achieved via a Mitsunobu reaction using bis(2,2,2-trifluoroethyl) malonate as nucleophile.     

A new bis(2,2,2-trifluoroethyl)phosphonate for the synthesis of Z-unsaturated N-methoxy-N-methylamides

The N-methoxy-N-methyl bis(2,2,2-trifluoroethyl)phosphonamide was easily obtained via the Arbuzov reaction with use of commercially available tris(2,2,2-trifluoroethyl)phosphite, 2-bromo-N-methoxy-N-methylacetamide, and KF/alumina. The reaction of bis(2,2,2-trifluoroethyl)phosphonate with several aldehydes demonstrates the versatility of the method, which gives Z-unsaturated amides in good yields.     

Synthesis of trifluoroethyl ethers from 2,2,2-trifluoroethyl chloride (HCFC-133a) in high temperature aqueous medium

Treatment of 2,2,2-trifluoroethyl chloride (HCFC-133a) with alcohols (phenols) and aqueous KOH in autoclave at 240-280 °C gives the corresponding 2,2,2-trifluoroethyl (2-chloro-1,1-difluoroethyl) ethers in good yields.     

Stereoselective formation of carbon-carbon bonds via SN2-displacement: synthesis of substituted cycloalkyl[b]indoles

A general asymmetric synthesis of substituted cycloalkyl[b]indoles has been accomplished. The key features of this approach are (1) the utilization of a Japp-Klingemann condensation/Fischer cyclization to prepare cycloalkyl[b]indolones, (2) the asymmetric borane reduction of these heterocyclic ketones with (S)-OAB to obtain enantiomerically pure alcohols, and (3) the stereoselective S(N)2-displacement of these indole alcohol substrates with a carbon nucleophile under Mitsunobu conditions to set the C1 or C3 tertiary carbon stereocenter. The use of trimethylphosphine (PMe3) and bis(2,2,2-trichloroethyl) azodicarboxylate (TCEAD) was found to have an effect on the Mitsunobu dehydrative alkylation.     

Borate esters as convenient reagents for direct amidation of carboxylic acids and transamidation of primary amides

Simple borates serve as effective promoters for amide bond formation with a variety of carboxylic acids and amines. With trimethyl or tris(2,2,2-trifluoroethyl) borate, amides are obtained in good to excellent yield and high purity after a simple work-up procedure. Tris(2,2,2-trifluoroethyl) borate can also be used for the straightforward conversion of primary amides to secondary amides via transamidation.     

O-Alkylation versus C-alkylation under Mitsunobu conditions

A comparative study of the Mitsunobu reaction at C1 and C6 positions of mannose using bis(2,2,2-trifluoroethyl) malonate as nucleophile is disclosed. While C-alkylation was predominant at the C6 position, only O-alkylation occurred at the anomeric position of the carbohydrate. Some factors playing a role in the selectivity of the reaction are discussed and an inverse mechanism of the Mitsunobu reaction for the anomeric position is proposed.     

Synthesis of poly(phenyltrifluoroethoxyphosphazene) by direct reaction of trimethylsilyl azide with bis(2,2,2-trifluoroethyl) phenylphosphonite

The reaction between bis(2,2,2-trifluoroethyl) phenylphosphonite and trimethylsilyl azide at temperatures from 70 to 120°C provides a mixture of bis(2,2,2-trifluoroethoxy)phenylN-(trimethylsilyl) phosphoranimine and poly(phenyl-2,2,2-trifluoroethoxyphosphazene). The polymer is probably formed by phosphine azide intermediates because the phosphor-animine is thermally stable up to 200°C. The polyphosphazene is an amorphous stereo-random polymer with a glass transition temperature at ?31°C.     

(E)-Selective Horner-Wadsworth-Emmons reaction of aryl alkyl ketones with bis(2,2,2-trifluoroethyl)phosphonoacetic acid

The stereoselective Horner-Wadsworth-Emmons reaction of aryl alkyl ketones with bis(2,2,2-trifluoroethyl)phosphonoacetic acid utilizing lithium hexamethyldisilazide in DMF afforded (E)-α,β-unsaturated carboxylic acids as the major products.     

Dehydrative C-H alkylation and alkenylation of phenols with alcohols: expedient synthesis for substituted phenols and benzofurans

A well-defined cationic Ru-H complex catalyzes the dehydrative C-H alkylation reaction of phenols with alcohols to form ortho-substituted phenol products. Benzofuran derivatives are efficiently synthesized from the dehydrative C-H alkenylation and annulation reaction of phenols with 1,2-diols. The catalytic C-H coupling method employs cheaply available phenols and alcohols, exhibits a broad substrate scope, tolerates carbonyl and amine functional groups, and liberates water as the only byproduct.     

Stereoselective synthesis of tetrasubstituted (Z)-alkenes from aryl alkyl ketones utilizing the Horner-Wadsworth-Emmons reaction

Tetrasubstituted (Z)-alkenes were readily prepared through the Horner-Wadsworth-Emmons reactions of methyl 2-[bis(2,2,2-trifluoroethyl)phosphono]propionate with aryl alkyl ketones by employing Sn(OSO(2)CF(3))(2) and N-ethylpiperidine.     

Z- and E-selective Horner–Wadsworth–Emmons reactions

In the present work, we determined and evaluated the stereochemical outcome of the Horner–Wadsworth–Emmons (HWE) reaction of 2-oxoalkylphosphonates with different ester functions (bis(2,2,2-trifluoroethyl), 2,2,2-trifluoroethyl methyl, dimethyl) and side chains (aliphatic, aromatic) with three different aldehydes (benzaldehyde, THP- and PPB-protected Corey aldehydes) under two reaction conditions. The “trans” protocol is generally used in the E-selective HWE reactions, while “cis” protocol promotes the Z-selectivity.     

A facile method for the stereoselective Horner-Wadsworth-Emmons reaction of aryl alkyl ketones

Excellent Z or E selectivity was observed in the Horner-Wadsworth-Emmons (HWE) reactions of methyl bis(2,2,2-trifluoroethyl)phosphonoacetate or ethyl 2-fluoro-2-diethylphosphonoacetate with aryl alkyl ketones bearing substituents on an aromatic moiety employing Sn(OSO2CF3)2 in the presence of N-ethylpiperidine.     

Atmospheric Chemistry and Environmental Assessment of Inhalational Fluroxene

Smog chamber/gas chromatography techniques are used to investigate the atmospheric degradation of fluroxene, an anesthetic, through oxidation with OH and Cl radicals at 298 K and under atmospheric pressure of N₂ or air. The measured rate constants (k) are: k(fluroxene+OH^.)=(2.96±0.61)×10⁻¹¹ and k(fluroxene+Cl^.)=(1.62±0.19)×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. The only product detected after the oxidation of fluroxene with OH radicals is 2,2,2-trifluoroethyl formate (79 % and 83 % molar yield in the absence and presence of NOx, respectively). However, after oxidation with Cl radicals, the detected products are 2,2,2-trifluoroethyl formate (78 %), 2,2,2-trifluoroethyl-1-chloroacetate (5 %), and chloroacetaldehyde (4 %), in the absence of NOx, and 2,2,2-trifluoroethyl formate (93 %), 2,2,2-trifluoroethyl-1-chloroacetate (6 %), and chloroacetaldehyde (5 %), in the presence of NOx. The results indicate that, both in the absence and presence of NOx, the main fate of fluroxene is the addition of the oxidant to the double bond and, once the alkoxy radical is formed, the main decomposition pathway is by means of degradation. Moreover, it is expected that 2,2,2-trifluoroethyl formate is the only oxidation product able to actively contribute to climate change. To successfully assess the contribution of fluroxene to global warming, we measure the infrared spectra of fluroxene and 2,2,2-trifluoroethyl formate, and calculate the radiative efficiencies (REs) to be 0.27 and 0.28 W m⁻² ppbv⁻¹, respectively. In addition, the cumulative effect owing to the formation of 2,2,2-trifluoroethyl formate is investigated, and the direct, indirect, and net global-warming potentials are calculated by using the REs and lifetimes of fluroxene and 2,2,2-trifluoroethyl formate.     

Some reactions of polyfluoroalkyl ethers and the preparation of bis(trifluorovinyl) ether

d1 and meso Bis (1,2,2-trifluoroethyl) ether and 1,1,2,2 tetrafluoroethyl 1,1,2-trifluoroethyl ether with aluminium halides or boron trichloride yield halogenopolyfluoroalkyl ethers. The epimerisation of the d1 and meso stereoisomers is discussed. Chlorination of bis (1,2,2-trifluoroethyl) ether and 1,1,2,2-tetrafluoroethyl 1,2,2-trifluoroethyl ether gives new chloropolyfluorodiethyl ethers and from bis (1,2-dichlorotrifluoroethyl) ether, bis (trifluorovinyl) ether is obtained by dechlorination.     

In-water dehydrative alkylation of ammonia and amines with alcohols by a polymeric bimetallic catalyst

An in-water dehydrative alkylation with a novel heterobimetallic polymeric catalyst is described. Thus, a boron-iridium heterobimetallic polymeric catalyst was prepared by ionic convolution of a poly(catechol borate) and an iridium complex. The alkylation of ammonia and amines with alcohols, alkylating agents, was performed with 1 mol % Ir of the heterogeneous catalyst in water without the use of organic solvents under aerobic conditions to give the corresponding alkylated amines.     

Synthesis and Potential Application of Novel C2-Symmetrical Bis（ferrocenyl） P2N Ligand

A novel chiral bis(ferrocenyl) P2N ligand 1 with C2-symmetry was synthesized through a four-step procedure from (R)-N,N-dimethyl-l-ferrocenylethylamine. In a model reaction of Pdcatalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate 6 with dimethyl malonate, good enantioselectivity (86% e.e.) was obtained.     

Development of an electrolytic system using solid-supported bases for in situ generation of a supporting electrolyte from methanol as a solvent

We have successfully developed a novel electrolytic system using solid-supported bases for in situ generation of a supporting electrolyte from methanol as a solvent. Anodic methoxylation of phenyl 2,2,2-trifluoroethyl sulfide using solid-supported bases was carried out to provide the alpha-methoxylated product in good to excellent yields. The alpha-methoxylated product and solid-supported bases were easily separated by only filtration, and the separated solid-supported bases were recyclable. Anodic methoxylation of phenyl 2,2,2-trifluoroethyl sulfide was successfully carried out 10 times by the recycling of silica gel-supported piperidine in good yields.     

Lipase-Catalyzed Polyester Synthesis

Abstract

The use of lipase as biocatalyst in polyesterification of aliphatic diacids or their derivatives, and diols in an organic solvent has been discussed. We have demonstrated that bis(2-chloroethyl) esters of succinic, fumaric, and maleic acid, and bis(2,2,2-trifluoroethyl) sebacate and -dodecanedioate can be polymerized by lipase-catalyzed polytransesterification. Maleate was isomerized to fumarate even under mild reaction conditions, resulting in poly(1,4-butyl fumarate). In order to obtain a high mass-average molar mass of the polyester, solid Mucor miehei lipase was found to be the best lipase and diphenyl ether the best solvent of several investigated. There was no clear relationship with the log P value of the solvent and the polyesterification activity of lipase. The highest degree of polymerization (DP = 184) of poly(1,4-butyl sebacate) with a mass-average molar mass of 46,600 g·mol^?1 was obtained in polytransesterification of bis(2,2,2-trifluoroethyl) sebacate and 1,4-butanediol using a programmed vacuum profile. However, a mass-average molar mass as high as about 42,000 g·mol^?1 (DP = 167) was also obtained with free sebacic acid when vacuum was employed to remove the water formed during esterification. The mass average molar mass of the polyester increased with an increase in the relative quantity of lipase up to 1 g per 1.5 mmol of diacid, with an increase in the molar mass of the aliphatic diol up to 1,5-pentanediol, and with an increase in the concentration of substrates up to 0.83 M.     

Catalyst‐Free Dehydrative α‐Alkylation of Ketones with Alcohols: Green and Selective Autocatalyzed Synthesis of Alcohols and Ketones

Direct dehydrative α‐alkylation reactions of ketones with alcohols are now realized under simple, practical, and green conditions without using external catalysts. These catalyst‐free autocatalyzed alkylation methods can efficiently afford useful alkylated ketone or alcohol products in a one‐pot manner and on a large scale by C?C bond formation of the in situ generated intermediates with subsequent controllable and selective Meerwein–Pondorf–Verley–Oppenauer‐type redox processes.     

Geminal dicarboxylates as carbonyl surrogates for asymmetric synthesis. Part II. Scope and applications.

An enantioselective synthesis of allylic esters has been achieved by a novel asymmetric alkylation of allylic gem-dicarboxylates. The catalyst derived from palladium(0) and R,R-1,2-di(2'-diphenylphosphinobenzamido)cyclohexene efficiently induced the alkylation process with a variety of nucleophiles to provide allylic esters as products in good yield. High regio- and enantioselectivities were observed in the alkylation with most nucleophiles derived from malonate, whereas a modest level of ee's was obtained in the reactions with less reactive nucleophiles such as bis(phenylsulfonyl)ethane. In the latter case, a slow addition procedure proved effective, leading to significantly improved ee's. The utility of the alkylation products was demonstrated by several synthetically useful transformations including allylic isomerizations, allylic alkylations, and Claisen rearrangements. Using these reactions, the chirality of the initial allylic carbon-oxygen bond could be transferred to new carbon-oxygen, carbon-carbon, or carbon-nitrogen bonds in a predictable fashion with high stereochemical fidelity. The conversion of gem-diesters to chiral esters by the substitution reaction is the equivalent of an asymmetric carbonyl addition by stabilized nucleophiles. In conjunction with the subsequent reactions that occur with high stereospecificity, allylic gem-dicarboxylates serve as synthons for a double allylic transformation.