Synthesis of 2-Aryl-3-trifluoromethylquinolines Using (E)-Trimethyl(3,3,3-trifluoroprop-1-enyl)silane

Ru(II)-Catalyzed Hydroarylation of in situ Generated 3,3,3-Trifluoro-1-propyne by C-H Bond Activation: A Facile and Practical Access to β-Trifluoromethylstyrenes

In this study, a practical and straightforward synthesis of β-(E)-trifluoromethylstyrenes by ruthenium-catalyzed C-H bond activation was developed. The readily available and inexpensive 2-bromo-3,3,3-trifluoropropene (BTP), a non-ozone depleting reagent, was used as a reservoir of 3,3,3-trifluoropropyne. With this approach, the monofunctionalization of a panel of heteroarenes was possible in a safe and scalable manner (23 examples, up to 87 % yield). Mechanistic investigations and density functional theory (DFT) calculations were also conducted to get a better understanding of the mechanism of this transformation. These studies suggested that 1) a cyclometallated ruthenium complex enabled the transformation, 2) this complex exhibited high efficiency in this transformation compared to the commercially available [RuCl2 (p-cymene)]2 and 3) the mechanism proceeded through a bis-cyclometallated ruthenium intermediate for the carboruthenation step.

Synthesis of Small Fluorescent Molecules and Evaluation of Photophysical Properties

A series of aniline-based fluorophores were newly synthesized. To increase their fluorescence quantum yields, it was particularly important to substitute 3,3,3-trifluoroprop-1-enyl (TFPE) groups next to the amino group to benefit from an extended π-electron delocalization. Among these, 5-CN-2-TFPE-aniline was found to behave as an excellent fluorophore with a reasonable fluorescence quantum yield of 0.89 even in aqueous solution. l-Alanine peptide, a nonfluorescent analogue of 5-CN-2-TFPE-aniline, was synthesized and successfully employed as an enzyme probe to detect aminopeptidase N activity.

[Approach for Producing New 3,3,3-Trifluoropropenylation Reagents: Introduction of a 3,3,3-Trifluoroprop-1-enyl Group for Drug Development]

The chemistry of the 3,3,3-trifluoroprop-1-enyl (TFPE) group has attractive characteristics in medicinal chemistry as a new fluorine motif. However, there are no reports on the properties of this group because it is difficult to construct molecules with it. For the convenient construction of the TFPE group, a new fluorination reagent, CF₃CH=CHTMS (1), was developed from commercially available chemicals with easy purification processes and excellent yields. The utility of 1 as a trifluoropropenylation reagent was exhibited in several types of reaction such as the Sonogashira cross-coupling reaction. Furthermore an indometacin analogue bearing a TFPE group showed greater pharmaceutical activity than the original indometacin. This review describes the details of these research studies under three topics: 1) synthesis of 1; 2) Sonogashira cross-coupling reaction of 1 with acetylene, followed by cyclization into an indole ring; and 3) synthesis of an indometacin analogue with a TFPE group.

Crystal Structure of (E)-2-(3,3,3-tri-fluoro-prop-1-en-1-yl)aniline

The mol-ecule of the title compound, C9H8F3N, adopts an E configuration with respect to the C=C double bond. The dihedral angle between the benzene ring and the prop-1-enyl group is 25.4 (3)°. In the crystal, mol-ecules are linked via pairs of N-H⋯F hydrogen bonds into inversion dimers with an R 2 2(16) ring motif. The dimers are linked by C-H⋯N hydrogen bonds, forming a ribbon structure along the b-axis direction. The ribbons are linked by N-H⋯π and C-H⋯π inter-actions, generating a three-dimensional network.

Development of a fluorogenic small substrate for dipeptidyl peptidase-4

A series of aniline and m-phenylenediamine derivatives with electron-withdrawing 3,3,3-trifluoropropenyl substituents were synthesized as small and chemically stable fluorescent organic compounds. Their fluorescence performances were evaluated by converting 2,4-disubstituted aniline 1 to the non-fluorescent dipeptide analogue H-Gly-Pro-1 for the use as a fluorogenic substrate for dipeptidyl peptidase-4 (DPP-4). The progress of the enzymatic hydrolysis of H-Gly-Pro-1 with DPP-4 was monitored by fluorometric determination of 1 released into the reaction medium. The results suggest that 1 could be used as fluorophore in OFF–ON-type fluorogenic probes.

Friedel-Crafts Alkylation of Arenes with 2-Halogeno-2-CF3-styrenes under Superacidic Conditions. Access to Trifluoromethylated Ethanes and Ethenes

The formation of the corresponding benzyl cations [ArHC(+)-CH(X)CF3] takes place under protonation of E-/Z-2-halogeno-2-CF3 styrenes [ArCH═C(X)CF3, X = F, Cl, Br] in superacids. The structures of these new electrophiles were studied by means of NMR and theoretical DFT calculations. According to these data, in the case of bromo derivatives, the formed cations, most probably, exist as cyclic bromonium ions; however, in the cases of chloro and fluoro derivatives, open forms are more preferable. Subsequent reaction of these benzyl cations with arenes proceeds as Friedel-Crafts alkylation to afford 1,1-diaryl-2-halo-3,3,3-trifluoropropanes [Ar(Ar')CH-CH(X)CF3] in high yields (up to 96%) as a mixture of two diastereomers. The prepared halogenopropanes were easily converted into the corresponding mixtures of E-/Z-trifluoromethylated diarylethenes [Ar(Ar')C═CCF3] (in yields up to 96%) by dehydrohalogenation with base (KOH or t-BuOK). The mechanism of elimination (E2 and Ecb) depends on the nature of the leaving group and reaction conditions.

A dramatic enhancing effect of InBr3 towards the oxidative Sonogashira cross-coupling reaction of 2-ethynylanilines

The addition of InBr3 to the oxidative Sonogashira cross-coupling reaction of 2-ethynylaniline with (E)-trimethyl(3,3,3-trifluoroprop-1-enyl)silane led to a dramatic increase in the reactivity to afford the corresponding 1,3-enynes bearing a trifluoromethyl group on their terminal sp(2) carbon. The subsequent cyclization of these 1,3-enynes under palladium catalysis provides access to the corresponding indoles bearing a 3,3,3-trifluoroprop-1-enyl group at their 2-position.

One-pot synthesis of 1,3-enynes with a CF3 group on the terminal sp2 carbon by an oxidative Sonogashira cross-coupling reaction

One-pot synthesis of 1,3-enynes with a CF₃ group on the terminal sp² carbon was achieved by an oxidative Sonogashira cross-coupling reaction with (E)-trimethyl(3,3,3-trifluoroprop-1-enyl)silane.

Oxidative 3,3,3-trifluoropropylation of arylaldehydes

A reaction between (E)-trimethyl(3,3,3-trifluoroprop-1-en-1-yl)silane (1) and arylaldehydes 2 was triggered by fluoride anions to afford aryl 3,3,3-trifluoropropyl ketones 3 in moderate to good yield. A mechanistic study of this reaction indicated that it occurred via an allyl alkoxide (4). A subsequent 1,3-proton shift of the benzylic proton of 4 forms 3. This reaction involves oxidative 3,3,3-trifluoropropylation of an arylaldehyde to afford 4,4,4-trifluoro-1-arylbutan-1-one.