Related Experiment Video
Updated: Jan 20, 2026

Constructing Cyclic Peptides Using an On-Tether Sulfonium Center
Published on: September 28, 2022
Construction of Complex Bisether-Bridged Medium-Sized Cyclic Compounds from o-(1-(Acyloxy)propargyl)benzaldehydes
1College of Chemistry , Beijing Normal University , Beijing 100875 , China.
Abstract:
We report herein our serendipitous discovery of the rapid and straightforward accesses to unprecedented diverse complex molecular structures from readily available starting materials. Catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene under mild conditions, o-(1-(acyloxy)propargyl)benzaldehydes 1 underwent efficient and selective dimerization reactions to produce novel complex bisether-bridged tricyclic products 3 and 4. The reactions proceeded most probably through dimerizations between 3-methylene-3H-isochromene intermediate and its zwitterionic resonance structures which were generated from a concerted 6-π electrocyclic ring closure reaction from the initially formed (2-formylphenyl)allene intermediates derived directly from o-(1-(acyloxy)propargyl)benzaldehydes. Treatment of the resulting product simply with NaOEt in ethanol and aqueous HCl, respectively, enabled further development of complex molecular diversities.
Related Concept Videos
Catalysis
Stereoisomerism of Cyclic Compounds
Lewis Acids and Bases
A coordinate covalent bond (or dative bond) occurs when one of the atoms in the bond provides both bonding electrons. For example, a coordinate covalent bond occurs when a water molecule combines with a hydrogen ion to form a hydronium ion. A coordinate covalent bond also results when...
Ions as Acids and Bases
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
Acids, Bases and Neutralization Reactions

