High-density polycycloalkanes were first produced with cellulose by a highly integrated route that features a selective hydrogenolysis of cellulose to 2,5hexanedione under mild conditions, followed by the direct synthesis of polycycloalkanes with 2,5-hexanedione and hydrogen over a dual-bed catalyst system. The polycycloalkane mixture as obtained has a high density (0.88 g mL À1 ) and low freezing point (225 K). In real application, they can be used as advanced aviation fuel or additives to improve the volumetric heat values of conventional aviation fuels.

This review comprehensively summarizes the advances achieved in catalytic intermolecular annulations of ynamides from 2010 to 2020.

A Schiff base-modified silver catalyst was developed for the direct carboxylation of terminal alkynes with CO2, enabling the efficient synthesis of valuable alkynyl carboxylic acids.

Decalin is the main component of JP-900, a thermally stable and high-energy density jet fuel. Decalin is also an important component of advanced jet fuels. Cyclopentanol is a platform compound that can be derived from lignocellulose. In this work, a mixture of C10 and C15 polycycloalkanes (with decalin as the major component) was first synthesized by the oligomerization/rearrangement of cyclopentene from the dehydration of cyclopentanol, followed by hydrogenation. Among the investigated catalysts, Amberlyst-36 resin demonstrated the highest activity and excellent stability for cyclopentanol dehydration and cyclopentene oligomerization/rearrangement. The influences of reaction temperature and reaction time on the catalytic performances of Amberlyst-36 resin for both reactions were investigated. Under the optimum conditions, 84.0% carbon yield of cyclopentene was obtained from cyclopentanol dehydration, and 74.2% carbon yield of C10 and C15 polycycloalkenes was achieved by the oligomerization/rearrangement of cyclopentene. Finally, the C10 and C15 polycycloalkenes from the oligomerization/rearrangement of cyclopentene were further hydrogenated to a mixture of C10 and C15 polycycloalkanes with decalin as the major component (77% selectivity). This polycycloalkane mixture has high density (0.896 g mL–1). As a potential application, it can be used as an additive to improve the volumetric calorific values of conventional biojet fuels.

A strategy for achieving diastereodivergent azidations of enynes has been developed, employing azide transfer from the M-N3 complex to alkyl radicals. Following this concept, the diastereoselectivity has been switched by modulating the transition metals and the ligands. The Mn(III)-mediated radical cyclization/azidation cascade of 1,7-enynes afforded trans-fused pyrrolo[3,4-c]quinolinones, whereas the Cu(II)/bipyridine system gave cis-products.

Depending on the reactant property and reaction mechanism, one major regioisomer can be favored in areaction that involves multiple active sites.H erein, an orthogonal regulation of nucleophilic and electrophilic sites in the regiodivergent hydroamination of isoprene with indazoles is demonstrated. Under Pd-hydride catalysis,t he 1,2-or 4,3insertion pathway with respect to the electrophilic sites on isoprene could be controlled by the choice of ligands.Interms of the nucleophilic sites on indazoles,t he reaction occurs at either the N 1-o rN 2-position of indazoles is governed by the acid co-catalysts.P reliminary experimental studies have been performed to rationalizet he mechanism and regioselectivity. This study not only contributes ap ractical tool for selective functionalization of isoprene,b ut also provides ag uide to manipulate the regioselectivity for the N-functionalization of indazoles.

The basic industrial feedstocki soprene was employed as ab uilding block to install prenyl and reverseprenyl groups onto indoles.T he regioselectivity can be manipulated by the choice of metal hydride.R everse-prenylated indoles were attained with high selectivity when using RhÀH. By switching to aP d ÀHc atalyst, selectivity toward prenylated indoles was achieved. This regiodivergent method also features high atom economy without stoichiometric byproduct formation.Scheme 4. Effects of boron additives on Pd-catalyzed prenylation.Scheme 5. Proposed mechanism for divergent selectivity.

An unprecedented TfNH-catalyzed formal [3 + 2] cycloaddition of ynamides with dioxazoles was developed to construct various polysubstituted 4-aminooxazoles. This approach features a metal-free catalytic bimolecular assembly of oxazole motifs, a low-cost catalyst, exceptionally mild reaction conditions, a very short reaction time, a broad substrate scope, and high efficiency. This metal-free protocol may find applications in pharmaceutical-oriented synthesis.