Measurement of the CKM angle γ using the B± → D*h± channels

A measurement of the CP-violating observables from B± → D*K± and B± → D*π± decays is presented, where D*(D) is an admixture of D*0 and D¯∗0 (D0 and D¯0) states and is reconstructed through the decay chains D*→ Dπ0/γ and D→KS0π+π−/KS0K+K−. The measurement is performed by analysing the signal yield variation across the D decay phase space and is independent of any amplitude model. The data sample used was collected by the LHCb experiment in proton-proton collisions and corresponds to a total integrated luminosity of 9 fb−1 at centre-of-mass energies of 7, 8 and 13 TeV. The CKM angle γ is determined to be 69−14+13∘ using the measured CP-violating observables. The hadronic parameters rBD∗K±, rBD∗π±, δBD∗K±, δBD∗π±, which are the ratios and strong phase differences between favoured and suppressed B± decays, are also reported

Synthesis of Oxaspiranic Compounds through [3 + 2] Annulation of Cyclopropenones and Donor–Acceptor Cyclopropanes

The Sc­(OTf)₃-catalyzed [3 + 2]-annulation reaction between cyclopropenones and donor–acceptor cyclopropanes is described. The process leads directly to the formation of 4-oxaspiro[2.4]­hept-1-ene derivatives in good to excellent reaction yields. Density functional theory calculations suggest that the [3 + 2]-annulation pathway is strongly preferred over the possible [3 + 3]-process

Synthesis of Oxaspiranic Compounds through [3 + 2] Annulation of Cyclopropenones and Donor–Acceptor Cyclopropanes

The Sc­(OTf)₃-catalyzed [3 + 2]-annulation reaction between cyclopropenones and donor–acceptor cyclopropanes is described. The process leads directly to the formation of 4-oxaspiro[2.4]­hept-1-ene derivatives in good to excellent reaction yields. Density functional theory calculations suggest that the [3 + 2]-annulation pathway is strongly preferred over the possible [3 + 3]-process

Two Complementary Approaches to Silicon-Supported Soluble [FeFe]-Hydrogenase Mimics

Two series of silicon-supported [(μ-SCH2)2NRFe2(CO)6] (R = p-OHC6H4, 3, and (CH2)2OH, 4a, and (CH2)5OH, 4b) hydrogenase mimics, as well as octamethylsilsesquioxane (POSS)-based nanostructures containing eight [(μ-SCH2)2NRFe2(CO)6] moieties, have been prepared either by reaction of the corresponding silyl and silyloxy chlorides and compounds 3 and 4 or by CuAAC between propargyl derivatives of silyl and silyloxy chlorides and azide 14. Cycloaddition between POSS-derived azide 23b and [(μ-SCH2)2NRFe2(CO)6] (R = alkyne) complexes 24 and 26 is efficient, leading to POSS-based nanostructures containing eight [(μ-SCH2)2NRFe2(CO)6] units. All of the complexes prepared through this work were soluble in organic solvents and hence fully characterizable by spectroscopic media. The electrochemistry of the linear siloxanes 6a and 10 is similar, with a reduction wave around −1.7 V, which is characteristic of these [(μ-SCH2)2NRFe2(CO)6] entities. Complexes 6a and 6b lacking 1,2,3-triazole moieties were electrochemically stable in the presence of AcOH, showing a strong electrocatalytic wave at −2.2 V, while complexes 16 and 18 having the 1,2,3-triazole ring decomposed but were electrocatalytically active in the wave at −2.2 V. POSS-[(μ-SCH2)2NRFe2(CO)6] derivatives 25 and 27 show a strong irreversible reduction event and are deposited in the electrode either when adding AcOH or over time (successive voltammograms). 29Si NMR shows that the integrity of the silicon cage is not affected by time or AcOH addition. These synthetic protocols and electrochemical studies will be applied in the design of silicon-supported [(μ-SCH2)2NRFe2(CO)6] mimics

Iron(III) Catalyzed Direct Synthesis of <i>cis</i>-2,7-Disubstituted Oxepanes. The Shortest Total Synthesis of (+)-Isolaurepan

Prins cyclization of <i>bis</i>-homoallylic alcohols with aldehydes catalyzed by iron(III) salts shows excellent <i>cis</i> selectivity and yields to form 2,7-disubstituted oxepanes. The iron(III) is able to catalyze this process with unactivated olefins. This cyclization was used as the key step in the shortest total synthesis of (+)-isolaurepan

Remote Control by π‑Conjugation of the Emissive Properties of Fischer Carbene-BODIPY Dyads

The synthesis, structure, and complete characterization of mono- and bimetallic dyads joining Fischer carbene complexes and BODIPY chromophores are reported. In these organometallic species, the Fischer carbene complex is attached to the BODIPY moiety through a <i>p</i>-aminophenyl group linked at the C8 carbon atom of the BODIPY core. The photophysical properties, namely the corresponding UV/vis absorption and emission spectra of these new metal–carbene complexes, are analyzed and discussed. It is found that whereas the absorption of the considered dyads strongly resembles that of the parent 4-anilinyl-substituted BODIPY, the fluorescence emission is significantly reduced in these species, very likely as a result of a Förster-type energy transfer mechanism. At variance, the replacement of the pentacarbonyl-metal(0) fragment by a carbonyl group leads to high fluorescence emission intensity. In addition, the emissive properties of the BODIPY core in these organometallic dyads can be tuned by remote groups by means of π-conjugation, as supported by density functional theory calculations

Effect of a κ¹‑Bonded-M-1,2,3-triazole (M = Co, Ru) on the Structure and Reactivity of Group 6 Alkoxy (Fischer) Carbenes

The [3 + 2] cycloaddition of two different metal-bound azides, [(Me₄cyclam)­Co^II(N₃)]­ClO₄ and (η⁵-C₅H₅)­(dppe)­Ru^II(N₃), (dppe = Ph₂PCH₂CH₂PPh₂) with Cr(0) and W(0) (ethoxy)­(alkynyl) Fischer carbenes has been efficiently used for the preparation of polymetallic metal-carbene complexes. The presence of the κ¹-bonded metal triazole causes a significant influence on the electronic properties, structure, and reactivity of this new class of Fischer alkoxycarbenes. For the Ru­(II) derivatives, their chemical behavior is considerably influenced by the interaction of the (η⁵-C₅H₅)­(dppe)­Ru^II-triazole moiety with the empty p-carbene orbital that provokes a noticeable decrease in the electrophilicity of the MC carbon (manifested by the shielding of the ¹³C NMR chemical shifts). In turn, in the Co­(II) derivatives, the incorporation of the (Me₄cyclam)­Co^II moiety diminishes the aromaticity of the triazole ring and has a marked effect on the energy and distribution of the LUSO orbital, mostly resident on the Co­(II) fragment. The almost negligible participation of the carbene moiety in the LUSO makes this position unable to react with nucleophiles. The reactions reported in this work constitute the first examples of [3 + 2] cycloaddition of azides and alkynyl Fischer carbene complexes in solution

Mono- and Bimetallic Zwitterionic Chromium(0) and Tungsten(0) Allenyls

A series of stable chiral (racemic), formally neutral, zwitterionic mono- and bimetallic M­(CO)₅[C­(OEt)CCR­(NHC)] (M = Cr, W) σ-allenyls are ready available by the addition of N-heterocyclic carbenes (NHCs) to Cr(0) and W(0) alkynyl Fischer carbene complexes. Different classes of NHCs, (e.g., 1,3-bis­(2,4,6-trimethylphenyl)­imidazol-2-ylidene, 1,3-bis­(2,4,6-trimethylphenyl)­imidazolin-2-ylidene, and their six- and seven-membered analogues and 1,3-bis­(dimethyl)­imidazol-2-ylidene) were employed as nucleophiles in these C–C bond-forming reactions yielding the novel complexes in essentially quantitative yields. A systematic experimental and computational study of the electronic properties of the Cr- and W-allenyls shows that their UV–vis spectra are directly influenced by the structure of the heterocyclic moiety derived from the NHC (ring size, substituents on the N atoms) and by the nature of the metal fragment (Cr/W). The electron-releasing nature of these complexes allows them to participate in electron-transfer reactions in the ground state, leading to a type of charged α,β-unsaturated Fischer carbenes that incorporate an NHC fragment in their structure