Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines

The reaction of racemic diarylmethylamines, (Ar¹Ar²CHNR₂), where Ar¹ is substituted with a 2-hydroxy group, with arylboroxines (Ar³BO)₃ in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar¹Ar²CH*Ar³) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through <i>o</i>-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents

Rhodium-Catalyzed Asymmetric Arylation/Defluorination of 1‑(Trifluoromethyl)alkenes Forming Enantioenriched 1,1-Difluoroalkenes

The reaction of 1-(trifluoromethyl)­alkenes (CF₃CH=CHR) with arylboroxines (ArBO)₃ in the presence of a chiral diene-rhodium catalyst gave high yields of chiral 1,1-difluoroalkenes (CF₂=CHC*HArR) with high enantioselectivity (≥95% ee). The reaction is assumed to proceed through β-fluoride elimination of a β,β,β-trifluoroalkylrhodium intermediate that is generated by arylrhodation of the 1-(trifluoromethyl)­alkene

Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines

The reaction of racemic diarylmethylamines, (Ar¹Ar²CHNR₂), where Ar¹ is substituted with a 2-hydroxy group, with arylboroxines (Ar³BO)₃ in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar¹Ar²CH*Ar³) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through <i>o</i>-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents

Asymmetric Synthesis of <i>P</i>‑Stereogenic Diarylphosphinites by Palladium-Catalyzed Enantioselective Addition of Diarylphosphines to Benzoquinones

The reaction of phenyl­(2,4,6-tri­methyl­phenyl)­phosphine with a substituted benzoquinone in the presence of a chiral phosphapalladacycle complex as a catalyst and triethylamine in chloroform at −45 °C proceeded in a new type of addition manner to give a high yield of a 4-hydroxyphenyl phenyl­(2,4,6-tri­methyl­phenyl)­phosphinite with 98% enantioselectivity, which is a versatile intermediate readily convertible into various phosphines and their derivatives with high enantiomeric purity

Asymmetric Synthesis of <i>P</i>‑Stereogenic Diarylphosphinites by Palladium-Catalyzed Enantioselective Addition of Diarylphosphines to Benzoquinones

The reaction of phenyl­(2,4,6-tri­methyl­phenyl)­phosphine with a substituted benzoquinone in the presence of a chiral phosphapalladacycle complex as a catalyst and triethylamine in chloroform at −45 °C proceeded in a new type of addition manner to give a high yield of a 4-hydroxyphenyl phenyl­(2,4,6-tri­methyl­phenyl)­phosphinite with 98% enantioselectivity, which is a versatile intermediate readily convertible into various phosphines and their derivatives with high enantiomeric purity

Palladacycle-Catalyzed Asymmetric Hydrophosphination of Enones for Synthesis of C*- and P*-Chiral Tertiary Phosphines

A highly reactive and stereoselective hydrophosphination of enones catalyzed by palladacycles for the synthesis of C*- and P*-chiral tertiary phosphines has been developed. When Ph₂PH was employed as the hydrophosphinating reagent, a series of C*-chiral tertiary phosphines were synthesized (C*–P bond formation) in high yields with excellent enantioselectivities, and a single recrystallization provides access to their enantiomerically pure forms. When racemic secondary phosphines <i>rac</i>-R³(R⁴)­PH were utilized, a series of tertiary phosphines containing both C*- and P*-chiral centers were generated (C*–P* bond formation) in high yields with good diastereo- and enantioselectivities. The stereoelectronic factors involved in the catalytic cycle have been revealed

Asymmetric Synthesis of Enaminophosphines via Palladacycle-Catalyzed Addition of Ph₂PH to α,β-Unsaturated Imines

A highly reactive, chemo- and enantioselective addition of diphenylphosphine to α,β-unsaturated imines catalyzed by a palladacycle has been developed, thus providing the access to a series of chiral tertiary enaminophosphines in high yields. A putative catalytic cycle has also been proposed

Asymmetric Synthesis of Enaminophosphines via Palladacycle-Catalyzed Addition of Ph₂PH to α,β-Unsaturated Imines

A highly reactive, chemo- and enantioselective addition of diphenylphosphine to α,β-unsaturated imines catalyzed by a palladacycle has been developed, thus providing the access to a series of chiral tertiary enaminophosphines in high yields. A putative catalytic cycle has also been proposed

Reactivity of Cycloplatinated Amine Complexes: Intramolecular C–C Bond Formation, C–H Activation, and PPh₂ Migration in Coordinated Alkynylphosphines

The monomeric <i>ortho</i>-platinated complexes [Pt­{R₁CH­(1-C₆H₄)­NMe₂-<i>C</i>,<i>N</i>}­{Ph₂PCCR₂}­Cl] (R₁ = Me, Et; R₂ = Me, Ph) with <i>trans</i>-<i>N,P</i> geometries were obtained regiospecifically from the reaction between the dimeric [Pt₂(μ-Cl)₂{R₁CH­(1-C₆H₄)­NMe₂-<i>C</i>,<i>N</i>}₂] and the corresponding alkynylphosphines in high yields. The phosphine complexes are highly stable in the solid state and in solution. However, in the presence of additional Pt­(II) ions, an intramolecular coupling reaction occurred in which a new carbon–carbon bond was formed between the aromatic γ-carbon of the <i>ortho</i>-platinated chiral phenylamine and the α-carbon of the (Ph₂P)–C_αC_β–(R₂) ligand. The (Ph₂P) moiety migrated to the neighboring β-carbon during the coupling reaction. By the judicious selection of the substituents on the alkynylphoshine along with deliberate introduction of selected chirality on the <i>ortho</i>-platinated phenylamine, the coupling reaction and the (Ph₂P) migration were found to proceed via an associative intramolecular mechanism that involves a Pt-vinylidene intermediate

data_sheet_1_Molecular Mechanisms for the Adaptive Switching Between the OAS/RNase L and OASL/RIG-I Pathways in Birds and Mammals.docx

<p>Host cells develop the OAS/RNase L [2′–5′–oligoadenylate synthetase (OAS)/ribonuclease L] system to degrade cellular and viral RNA, and/or the OASL/RIG-I (2′–5′–OAS like/retinoic acid inducible protein I) system to enhance RIG-I-mediated IFN induction, thus providing the first line of defense against viral infection. The 2′–5′–OAS-like (OASL) protein may activate the OAS/RNase L system using its typical OAS-like domain (OLD) or mimic the K63-linked pUb to enhance antiviral activity of the OASL/RIG-I system using its two tandem ubiquitin-like domains (UBLs). We first describe that divergent avian (duck and ostrich) OASL inhibit the replication of a broad range of RNA viruses by activating and magnifying the OAS/RNase L pathway in a UBL-dependent manner. This is in sharp contrast to mammalian enzymatic OASL, which activates and magnifies the OAS/RNase L pathway in a UBL-independent manner, similar to 2′–5′–oligoadenylate synthetase 1 (OAS1). We further show that both avian and mammalian OASL can reversibly exchange to activate and magnify the OAS/RNase L and OASL/RIG-I system by introducing only three key residues, suggesting that ancient OASL possess 2–5A [p_x5′A(2′p5′A)_n; x = 1-3; n ≥ 2] activity and has functionally switched to the OASL/RIG-I pathway recently. Our findings indicate the molecular mechanisms involved in the switching of avian and mammalian OASL molecules to activate and enhance the OAS/RNase L and OASL/RIG-I pathways in response to infection by RNA viruses.</p