Refernces
10.1021/jo951643d
The study investigates the semi-π analogue of double hyperconjugation, known as "hyperconjugation/conjugation," in 4-isopropylidenecyclohexyl mesylate (4-OMs) and compares it with the saturated analogue, trans-4-isopropylcyclohexyl mesylate (5-OMs). The researchers found that the unsaturated substrate 4-OMs reacts only four times faster than the saturated substrate 5-OMs in 97% trifluoroethanol, indicating no significant through-bond interaction of the double bond with the reactive center. This is attributed to less than ideal overlap of the γ,δ π orbitals with the R, σ orbitals. However, when an electron-rich tin atom is attached to the 4-position, it provides a large rate enhancement and changes the mechanism to carbocation formation through double hyperconjugation. The study concludes that the π bond does not effectively stabilize positive charge through two stages of conjugation in the studied system, suggesting that the hyperconjugation/conjugation mode may not be a viable mechanism under the given conditions.
10.1016/j.mcat.2020.111345
The research primarily focuses on the development of an eco-friendly electrochemical method for synthesizing quinazolin-4(3H)-one derivatives, utilizing α-keto acids and 2-aminobenzamides as reactants. The process eliminates the need for homogeneous metal catalysts, bases, or external oxidants and operates under mild conditions with CO2 as a by-product. The experiments involved optimizing reaction conditions, such as the use of a platinum electrode setup, constant current, and 2,2,2-trifluoroethanol as the solvent with Bu4NPF6 as the electrolyte, resulting in a 90% yield of the desired product. The substrate scope was explored with various α-keto acids and 2-aminobenzamides, yielding a range of 2,3-disubstituted quinazolinone products. Control experiments confirmed the necessity of electric current and the involvement of radical species, suggesting a possible reaction mechanism involving anodic oxidation and decarboxylation steps.
10.1021/co300046r
The research focuses on the development of a one-pot, two-step protocol for synthesizing a variety of novel polycyclic heterocycles with high skeletal diversity, characterized by the presence of embedded or attached benzimidazole and often a ring system formed through lactamization. The study utilizes the Ugi multicomponent reaction (MCR) combined with an acid-mediated cyclodehydration step. Reactants include keto- or formyl acids, N-Boc-diamines, and isocyanides, which are combined in trifluoroethanol (TFE) as the solvent. The Ugi reaction is monitored using LCMS, and after completion, the product is subjected to a treatment with trifluoroacetic acid (TFA) in dichloroethane (DCE) and microwave irradiation to promote cyclodehydration, resulting in the formation of tricyclic scaffolds with an α-quaternary methyl group. The experiments yield a range of unique scaffolds with excellent physicochemical properties, demonstrating the versatility and efficiency of the protocol. The analysis of the products includes purification using a CombiFlash Rf system and X-ray crystallographic analysis for structural elucidation, confirming the successful synthesis of the desired polycyclic heterocycles.
10.1021/ja00317a032
The research investigates the reactivity and selectivity of substituted 1-phenylethyl carbocations with various nucleophilic reagents, including alcohols, water, and oxygen anions. The purpose of the study was to determine the selectivities of these carbocations towards different nucleophiles and to understand how these selectivities change as the carbocation's reactivity increases. The research concluded that the selectivity for activation-limited reactions decreases with increasing carbocation reactivity, which contrasts with the behavior expected from the NC scale of reactivity. Notably, the study found that the 1-(4-(dimethylamino)phenyl)ethyl carbocation exhibited high selectivity in its reactions with alcohols. The chemicals used in this process included a range of substituted 1-phenylethyl derivatives, nucleophilic reagents such as alcohols, water, and oxygen anions, as well as various leaving groups to generate the carbocations. The study also utilized solvents like trifluoroethanol and water mixtures to control the reactions and analyze the products.
10.1021/jo951439q
The research investigates the intramolecular cyclization of phenol derivatives bearing aminoquinones using a hypervalent iodine reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA), with the aim of preparing novel antitumor compounds. The study selectively obtained azacarbocyclic spirodienone derivatives or phenol derivatives containing the 2,3-dihydro-1H-azepine systems by reacting ortho- or meta-substituted phenol derivatives with PIFA in 2,2,2-trifluoroethanol. The findings confirm the difference in reactivities between ortho- and meta-substituted phenol derivatives protected by methyl or silyl groups, allowing for the selective synthesis of pharmacologically important compounds.
10.1246/bcsj.72.163
The study investigates the solvolysis reactions of phenyl[(E)-styryljiodonium tetrafluoroborate (1) in various solvents, focusing on the products, reaction rates, and mechanisms involved. The primary chemicals used are phenyl[(E)-styryljiodonium tetrafluoroborate as the substrate, and different solvents including methanol, ethanol, 2,2,2-trifluoroethanol (TFE), and acetic acid. The study also employs labeled substrates, such as the α-deuterated substrate (1-αD), to analyze the reaction mechanisms. The reactions involve α-elimination and substitutions with configurational retention and inversion. In methanol and ethanol, α-elimination is the main reaction, producing phenylacetylene (3) as the major product, while substitution reactions become more significant in less basic solvents like acetic acid and TFE. The study finds that the reaction rates and the fraction of α-elimination decrease as the solvent basicity decreases. The substitution mechanism is concluded to involve parallel pathways: an SN1-type with a vinylenebenzenium ion intermediate leading to retention and a vinylic SN2-type with a direct attack by the nucleophilic solvent leading to inversion.
10.1021/ol050558h
The research focuses on the synthesis of D- and L-1,4,6-trideoxy-4,4-difluoronojirimycin, a novel series of gem-difluoromethylenated azasugars. The synthesis involves 10 steps starting from trifluoroethanol, with key chemicals including trifluoroethanol, LDA (lithium diisopropylamide), formaldehyde, MEMCl (2-methoxyethoxymethyl chloride), mesyl chloride, NaN3 (sodium azide), Pd(PPh3)4 (tetrakis(triphenylphosphine)palladium(0)), PPh3 (triphenylphosphine), CbzCl (benzyl chloroformate), SOCl2 (thionyl chloride), and (DHQ)2PHAL or (DHQD)2PHAL (chiral ligands for Sharpless asymmetric dihydroxylation). The synthesis process includes multiple steps such as protection, elimination, vinyl anion formation, sigmatropic rearrangement, allylic substitution, imine formation, Sharpless asymmetric dihydroxylation, and hydrogenation. The final products are obtained with good diastereoselectivity and enantiomeric excess, demonstrating the effectiveness of the synthetic route.
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