Ag-Catalyzed cross-dehydrogenative-coupling for the synthesis of 1,4-dioxan-2-yl substituted quinazoline hybrids in an aqueous medium

We herein developed an effective approach for the construction of 2- or 4-(1,4-dioxan-2-yl) substituted quinazolines under mild conditions. A silver-K2S2O8 catalyzed direct CDC reaction between quinazolines and 1,4-dioxane for the synthesis of a series of 2- or 4-(1,4-dioxan-2-yl) substituted quinazoline hybrids is reported. The reaction proceeded well in water under mild conditions and showed a broad substrate scope and good functional group compatibility.

Alcohols as Substrates in Transition-Metal-Catalyzed Arylation, Alkylation, and Related Reactions

Alcohols are abundant and attractive feedstock molecules for organic synthesis. Many methods for their functionalization require them to first be converted into a more activated derivative, while recent years have seen a vast increase in the number of complexity-building transformations that directly harness unprotected alcohols. This Review discusses how transition metal catalysis can be used toward this goal. These transformations are broadly classified into three categories. Deoxygenative functionalizations, representing derivatization of the C-O bond, enable the alcohol to act as a leaving group toward the formation of new C-C bonds. Etherifications, characterized by derivatization of the O-H bond, represent classical reactivity that has been modernized to include mild reaction conditions, diverse reaction partners, and high selectivities. Lastly, chain functionalization reactions are described, wherein the alcohol group acts as a mediator in formal C-H functionalization reactions of the alkyl backbone. Each of these three classes of transformation will be discussed in context of intermolecular arylation, alkylation, and related reactions, illustrating how catalysis can enable alcohols to be directly harnessed for organic synthesis.

Visible Light-Induced Unactivated δ-C(sp3 )-H Amination of Alcohols Catalyzed by Iron

An iron-catalyzed remote C(sp³ )-H amination of alcohols through 1,5-hydrogen atom transfer is developed. This protocol provides a method to generate δ-C(sp³ )-N bonds from primary, secondary, and tertiary alcohols under mild conditions. A wide substrate scope and a good functional group tolerance are presented. Mechanistic studies show that a LMCT course of an Fe-OR species and a chlorine radical-induced hydrogen abstraction of an alcohol are possible to generate the alkoxy radical intermediate.

Electrochemical Oxidative C-H Arylation of Quinoxalin(on)es with Arylhydrazine Hydrochlorides under Mild Conditions

A practical and scalable protocol for electrochemical arylation of quinoxalin(on)es with arylhydrazine hydrochlorides under mild conditions has been developed. This method exhibits high efficiency, easy scalability, and broad functional group tolerance. Various quinoxalin(on)es and arylhydrazines underwent this transformation smoothly in an undivided cell, providing the corresponding aryl-substituted quinoxalin(on)es in moderate to good yields. A radical mechanism is involved in this arylation reaction.

Ag-Catalyzed Remote Unactivated C(sp3)-H Heteroarylation of Free Alcohols in Water

Catalyzed by silver salt, the unactivated C(sp³)-H heteroarylation of free alcohol at the δ position is realized under gentle thermal conditions in water through a radical procedure. Both protonic acids and Lewis acids are found to be efficient for activating pyridines for this Minisci-type reaction. The reaction enjoys a good functional group tolerance and substrate scope. Terminal secondary and tertiary alcohols are suitable substrates. With either electron-donating or -withdrawing groups, the electron-deficient heteroarene substrates generate the target products in moderate to good yields. A gram-scale experiment can be successfully operated. A radical blocking experiment and a radical clock experiment are studied to support the radical mechanism.