Two new chemically stable [acid and base] 2D crystalline covalent organic frameworks (COFs) (TpPa-1 and TpPa-2) were synthesized using combined reversible and irreversible organic reactions. Syntheses of these COFs were done by the Schiff base reactions of 1,3,5-triformylphloroglucinol (Tp) with p-phenylenediamine (Pa-1) and 2,5-dimethyl-p-phenylenediamine (Pa-2), respectively, in 1:1 mesitylene/dioxane. The expected enol-imine (OH) form underwent irreversible proton tautomerism, and only the keto-enamine form was observed. Because of the irreversible nature of the total reaction and the absence of an imine bond in the system, TpPa-1 and TpPa-2 showed strong resistance toward acid (9 N HCl) and boiling water. Moreover, TpPa-2 showed exceptional stability in base (9 N NaOH) as well.

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A strategy for expedient synthesis of 3-substituted chromones from easily available o-hydroxyaryl­enaminones and diazo compounds has been developed. Carefully conducted experimental and computational studies led us to propose an uncommon mechanistic pathway involving the hydroxyl group assisted alkylation of enaminones with in situ generated gold carbenes.

The temperature dependent selectivity switch in the reaction of arynes with aliphatic alcohols in THF has been reported. At -20 °C, arynes smoothly insert into the O-H bond of alcohols to form alkyl aryl ethers. Interestingly, at 60 °C, a highly selective multicomponent coupling occurs with the solvent THF acting as the nucleophilic trigger affording (4-(alkoxy)butoxy)arenes.

Selectively converting linear alkanes to α-olefins under mild conditions is a highly desirable transformation given the abundance of alkanes as well as the use of olefins as building blocks in the chemical community. Until now, this reaction has been primarily the remit of noble-metal catalysts, despite extensive work showing that base-metal alkylidenes can mediate the reaction in a stoichiometric fashion. Here, we show how the presence of a hydrogen acceptor, such as the phosphorus ylide, when combined with the alkylidene complex (PNP)Ti=CHBu(CH) (PNP=N[2-P(CHMe)-4-methylphenyl]), catalyses the dehydrogenation of cycloalkanes to cyclic alkenes, and linear alkanes with chain lengths of C to C to terminal olefins under mild conditions. This Article represents the first example of a homogeneous and selective alkane dehydrogenation reaction using a base-metal titanium catalyst. We also propose a unique mechanism for the transfer dehydrogenation of hydrocarbons to olefins and discuss a complete cycle based on a combined experimental and computational study.