Pyrogallarene shows concentration-dependent instability in dilute solutions resulting in elimination of two ketene molecules and formation of pyrogallarene lactones. This unexpected phenomenon, which is not observed with resorcinarenes, highlights the significance of the four hydroxyl groups at 2-position for the molecular characteristics of pyrogallarenes.

A concise approach to the algal metabolite 1 is described, which also determines the previously unknown stereostructure of this natural product. Compound 1 is distinguished by a rare brominated 4-pyrone nucleus linked as a ketene-acetal to a polyunsaturated macrocyclic scaffold comprising an extra homoallylic bromide entity. The synthesis of 1 is based on the elaboration and selective functiona...

The photochemistry of ortho-nitrobenzaldehyde dissolved in tetrahydrofuran was studied by means of femtosecond UV/Vis and IR spectroscopy. Comparison was made of the spectral and temporal signatures for ~400 nm and ~260 nm excitation. The 400 nm excitation promotes NBA to its lowest excited singlet state of nπ* character whereas for 260 nm an upper excited state of ππ* character is addressed. O...

An efficient and straightforward four-component synthetic protocol has been developed to synthesize imidazo[1,2-a]pyridines and imidazo[1,2,3-ij][1,8]naphthyridine derivatives incorporating medicinally privileged heterosystems from heterocyclic ketene aminals, aldehydes, diketene, and amines via cascade reactions, including diketene ring-opening, Knoevenagel condensation, aza-ene reaction, imin...

The cycloaddition reaction of acylketenes with vinyl ethers affords an extremely direct route to 2,6-dideoxysugars and their methyl ethers. The lithium enolate of commercial 2,6,6-trimethyldioxinone 3 was fluorinated in good yield to afford fluorinated dioxinone 8. An illustrative range of fluorinated 2,6-dideoxysugar derivatives was prepared via the acetyl ketene-vinyl ether cycloadduct. Elect...

Two cycloaddition reactions were utilized for the construction of the 5,6,7-tricyclic skeleton of lancifodilactone F and buxapentalactone. A [2+2] ketene cycloaddition reaction was first used to set their adjacent all-carbon quaternary centers at the 5,6-ring junction. An arene-olefin meta-photocycloaddition reaction was then used to install the 6- and 7-membered rings concurrently.

It has been revealed for the first time that co-promoted by CuCl and NaH in the presence of molecular oxygen (air), the reaction of dicinnamoyl ketene dithioacetals as the acyclic C6 synthons with ethyl cyanoacetate gives functionalized seven-membered carbocycles. A mechanism is proposed involving a tandem Michael addition-intramolecular radical cyclization-benzyl C(sp(3))-H bond oxidation.