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The known boranes (R(Me

A regioselective addition of alkynylsilanes across unactivated, terminal alkenes is reported. The reaction is initiated by the capture of a sterically unhindered silylium ion by a silylated phenylacetylene derivative to form a bis(silylated) ketene-like carbocation. This in situ-generated key intermediate is the actual catalyst that maintains the catalytic cycle by a series of electrophilic addition reactions of silylium ions and β-silicon-stabilized carbocations. The computed reaction mechanism is fully consistent with the experimental findings. This unprecedented two-component carbosilylation establishes a C(sp

Transmission coefficient through a slit normalized to the power couple to the cavity.

Asian Americans Pacific Islanders (AAPI) share a disproportionate burden of chronic hepatitis B (CHB) in both the United States and New York State. Current hepatitis B virus (HBV) screening and research efforts have focused on urban communities. We administered a cross-sectional survey to 64 attendants at two free health fairs hosted by AAPI organizations on suburban Long Island, New York. We report the demographic make-up, healthcare attitudes, and HBV-related health histories of event attendees in Nassau and Suffolk Counties. Participants in Nassau County generally had more access to healthcare (97.1% vs 74.1% insured, 91.4% vs. 63.0% annual physician visit) and more familiarity with HBV screening (57.1% vs 17.2% history of HBV screening, 42.9% vs 3.9% physician recommendation for HBV screening). AAPI are a heterogenous population. Communities in close proximity may be demographically distinct and efforts to screen for HBV should be tailored to individual communities.

FLPs, R2POBcat (R = tBu 1, Mes 2), are readily derived from the reactions of the corresponding phosphine oxides, nBuLi and ClBcat. Despite the poor Lewis acidity of boron, these species react with PhOH, CO2, CS2, PhNCO, MesCNO, O2, 9,10-phenanthrenedione, and diazomethanes to effect FLP addition reactions affording a series of heterocycles. The reaction of 1 with EtO2CCHN2 gives the bicyclic product, EtO2CCHN2(tBu2POBcat)2. High-level DFT calculations reveal that these cyclization processes proceed via 1,1-addition to the terminal N of diazomethane followed by 1,2-boron-migration affording the five membered rings. The reaction of the EtO2CCHN2 derivative with the second equivalent of FLP 1 is attributed to less steric demands.

Es wird über eine metallfreie, intermolekulare syn-Addition von Hexamethyldisilan an einfache Alkene berichtet. Der Katalysezyklus wird durch die Übertragung einer Methylgruppe des Disilans auf eine Silyliumion-artige Zwischenstufe eingeleitet und aufrechterhalten, was der (Neu)bildung des Silyliumion-Katalysators gleichkommt. Das Hauptmerkmal der Reaktionssequenz ist die Spaltung der Si-Si-Bindung im Zuge einer 1,3-Silylwanderung von Silicium nach Kohlenstoff. Eine zentrale Zwischenstufe der Katalyse wurde durch Röntgenbeugung strukturell charakterisiert, und der berechnete Reaktionsmechanismus steht in vollständigem Einklang mit den experimentellen Befunden.

A transition-metal-free hydrothiolation of 1,3-dienes for the synthesis of secondary and tertiary allylic sulfides is reported. The boron Lewis acids tris(pentafluorophenyl)borane, B(C6F5)3, and BF3·Et2O are shown to catalyze the regioselective hydrothiolation of a wide range of terminal 1-aryl-1,3-dienes. In the case of internal 1,3-dienes, B(C6F5)3 is by far the better catalyst than BF3·Et2O. The process features mild reaction conditions, broad scope, and low catalyst loading, and it can be scaled up quickly over a short reaction time. The reactions are rate-limited by the 1-aryl-directed protonation of 1,3-dienes with thiol-boron Lewis acid complexes, followed by sulfide anion transfer to the resultant allyl cations, as revealed by high-level DFT calculations.

While (Ph2CN2)B(C6F5)3 is unstable, single electron transfer from Cp*2Co affords the isolation of stable products [Cp*2Co][Ph2CNNHB(C6F5)3] 1 and [Cp*Co(C5Me4CH2B(C6F5)3)] 2. The analogous combination of Ph2CN2 and BPh3 showed no evidence of adduct formation and yet single electron transfer from Cp*2Cr affords the species [Cp*2Cr][PhC(C6H4)NNBPh3] 3 and [Cp*2Cr][Ph2CNNHBPh3] 4. Computations showed both reactions proceed via transient radical anions of the diphenyldiazomethane–borane adducts to effect C−H bond activations., Single electron transfer to diphenyldiazomethane–borane adducts generates transient radical anions that effect C−H bond activations. Such reductions provide a strategy to stabilize weak and even undetectable donor–acceptor adducts.

Aiming at the problem of contact operation of manipulator with uncertain model, a compliant control method was proposed and verified by experiments. When the manipulator contacts with the environment, the force needs to be controlled stably and accurately. If the force is too small, the mission may fail, otherwise it will damage the equipment. Considering that the parameters of the manipulator are not ascertained, the adaptive control method is introduced to solve the problem of control. Taking a typical plug task as an example, the effectiveness of the compliance control method is verified by comparing several groups of experiments. This method is helpful to improve the robustness and intelligence of the manipulator, expand its working range and adaptability.