Allylic Substitution for Construction of a Chiral Quaternary Carbon Possessing an Aryl Group

Phenylcopper reagents derived from 2:1 PhMgBr/Cu­(acac)₂ and 3:1:1 PhMgBr/Cu­(acac)₂/ZnI₂ were found to be highly reactive and regioselective in the allylic substitution of γ,γ-disubstituted secondary allylic picolinates designed for construction of a quaternary carbon, whereas the previous 2:1 ArMgBr/CuBr·Me₂S reagent and that with ZnX₂ were unsuccessful. The generality of the ArMgBr/Cu­(acac)₂ reagent was examined with enantiomerically enriched allylic picolinates, which furnished quaternary carbons with high efficiency in >92% regioselectivity and >97% chirality transfer. Two cyclohexanes with a quaternary carbon were synthesized by using these reagents

Oxidant-Free Rh(III)-Catalyzed Direct C–H Olefination of Arenes with Allyl Acetates

Rh(III)-catalyzed direct olefination of arenes with allyl acetate <i>via</i> C–H bond activation is described using <i>N,N</i>-disubstituted aminocarbonyl as the directing group. The catalyst undergoes a redox neutral process, and high to excellent yields of <i>trans</i>-products are obtained. This protocol exhibits a wide spectrum of functionality compatibility because of the simple reaction conditions employed and provides a highly effective synthetic method in the realm of C–H olefination

Divergent Functionalization of Indoles with Acryloyl Silanes via Rhodium-Catalyzed C–H Activation

A protocol enabled by rhodium-catalyzed C–H functionalization of indoles with acryloyl silanes was developed, providing a convenient and highly effective method for the synthesis of functionalized acylsilane derivatives. By tuning the reaction condition, this C–H-activation-initiated reaction proceeds divergently with acryloyl silianes to selectively afford alkylation or alkenylation products via hydroarylation or oxidative cross-coupling, respectively. The mild reaction conditions employed in both cases enable the tolerance of a wide scope of functionalities as well as high reaction efficiency. Furthermore, polycyclic indole derivatives were easily accessed from 2-alkenylation products through a visible-light-induced reaction cascade

Rhodium(III)-Catalyzed Olefinic C–H Alkynylation of Acrylamides Using Tosyl-Imide as Directing Group

The Rh­(III)-catalyzed C–H alkynylation of acrylamide derivative is realized using a hypervalent alkynyl iodine reagent. The use of a weakly coordinating directing group proved to be of critical importance. This reaction displays broad functional group tolerance and high efficiency, which opens a new synthetic pathway to access functionalized 1,3-enyne skeletons

A model-guided symbolic execution approach for network protocol implementations and vulnerability detection

<div><p>Formal techniques have been devoted to analyzing whether network protocol specifications violate security policies; however, these methods cannot detect vulnerabilities in the implementations of the network protocols themselves. Symbolic execution can be used to analyze the paths of the network protocol implementations, but for stateful network protocols, it is difficult to reach the deep states of the protocol. This paper proposes a novel model-guided approach to detect vulnerabilities in network protocol implementations. Our method first abstracts a finite state machine (FSM) model, then utilizes the model to guide the symbolic execution. This approach achieves high coverage of both the code and the protocol states. The proposed method is implemented and applied to test numerous real-world network protocol implementations. The experimental results indicate that the proposed method is more effective than traditional fuzzing methods such as SPIKE at detecting vulnerabilities in the deep states of network protocol implementations.</p></div

Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder

Employment of fluorophore-tagged alkyl and aryl iodides permitted detection of persistent surface intermediates during their direct insertion to commercially available zinc powder. The sensitivity of this subensemble microscopy technique enabled structure–reactivity studies in the formation of intermediates that are present in quantities sufficiently low as to have been undetected previously by traditional ensemble analytical techniques. These surface intermediates were transformed by lithium chloride, leading to the assignment of the mechanistic role of lithium chloride as changing the rate-determining step in the reaction by lowering the barrier for solubilization of these otherwise persistent surface organometallic intermediates. The temperature dependence/qualitative barrier of the direct insertion step was determined independently from the solubilization step and from the barrier for the overall reaction. Detection of these zinc surface intermediates at the single-molecule level, i.e., of individual surface organometallic species, has been achieved for the first time. Energy dispersive X-ray spectroscopy (EDS) measurements of the elemental composition of the surface of the zinc powder determined that lithium chloride does not clean the surface of the oxides; instead, pretreatment of the surface with TMSCl effects partial removal of surface oxides after the 2 h pretreatment time previously reported in the empirically optimized synthetic procedure. Current limitations of this microscopy approach are also determined and discussed with respect to the addition of solid reagents during in operando imaging. Characterization of the resulting soluble fluorophore-tagged organozinc/LiCl complex by ¹H NMR spectroscopy, mass spectrometry, and fluorescence spectroscopy provided insight into its solution dynamics and chemical exchange processes

Framework of the proposed method.

<p>Framework of the proposed method.</p

Protocol vulnerability detection based on network traffic analysis and binary reverse engineering

<div><p>Network protocol vulnerability detection plays an important role in many domains, including protocol security analysis, application security, and network intrusion detection. In this study, by analyzing the general fuzzing method of network protocols, we propose a novel approach that combines network traffic analysis with the binary reverse engineering method. For network traffic analysis, the block-based protocol description language is introduced to construct test scripts, while the binary reverse engineering method employs the genetic algorithm with a fitness function designed to focus on code coverage. This combination leads to a substantial improvement in fuzz testing for network protocols. We build a prototype system and use it to test several real-world network protocol implementations. The experimental results show that the proposed approach detects vulnerabilities more efficiently and effectively than general fuzzing methods such as SPIKE.</p></div

Description of FTP protocol based on block-based language.

<p>Description of FTP protocol based on block-based language.</p

An example of symbolic execution example flow diagram.

<p>An example of symbolic execution example flow diagram.</p