Doubly Bridged Biscyclopropenones, a New Family of Phanes

Abstract

The first representatives, 10-12, of the new species of double-decked cyclopropenonophanes were synthesized by cycloaddition reactions of dichlorocarbene to alkynylenecyclopropenonophanes 7-9 followed by hydrolysis as well as in an alternative route involving hydride abstraction from dichlorotricycloalkadienes 16 and 17 to dichlorocyclopropenyliophanes and in situ hydrolysis of the latter. The X-ray analysis of [3.3]cyclopropenonophane 10 reveals a considerable tetragonalization of the bridgehead carbon atoms, indicating a significant deformation of the cyclopropenone moieties in the phane corset. According to ab initio calculations, the π orbitals of the cyclopropenones display transannular interactions of nearly the same scale as found in 7.

Selenium- and Tellurium-Substituted Cyclopropenones and their Facile Ring-Opening with Methanol

“…Treatment of the selenium‐ and tellurium‐substituted cyclopropenones with excess methanol in dichloromethane at room temperature quantitatively afforded the corresponding α,β‐unsaturated esters 5a 13 and 5b (Scheme ). No such facile ring‐opening reaction is known for alkyl‐substituted derivatives, which can be treated with alcohols without decomposition 14.…”

Tethered Dithiacyclopropenones. Syntheses and Structural Properties of Tetrathiacyclopropenonophanes

“…In the most of these cases the aromatic building blocks were either the well-known five-membered 6π-heterocycles, benzene and larger benzenoid and nonbenzenoid aromatic systems. − Cyclophanes with rings smaller than five have been investigated relatively late . Cyclophanes with cyclopropenone rings as building blocks have become available from cyclic diynes and carbenes (see Scheme ) . However, the yields, especially of double-decked [ n .…”

“…However, the yields, especially of double-decked [ n . n ]cyclopropenonophanes were low due to a number of side reactions 7 which are partly due to the kinetic instability of the cyclopropenone ring and partly to the activation of the reactivity of the methylene groups next to the cyclopropenone ring 7a. The kinetic stability of the cyclopropenone ring system can be increased by substitution with electron-donating or bulky groups.…”

“…We recently reported a series of compounds in which two cyclopropenone rings were tethered by alkyl chains ( 3 ). These cyclophanes were available via a two-step sequence 7b. In the first step one triple bond of the diyne 1 was reacted with chloroform/ n -butyllithium in THF at −78 °C followed by hydrolysis to yield 2 .…”

Photoswitchable enediynes: use of cyclopropenone as photocleavable masking group for the enediyne triple bond

“…14,15 In case of diynes, this procedure allows to avoid the formation of bis-adducts even in the presence of excess of the reagent. 16 Other methods for the in situ generation of dichlorocabenes often produce substantial amounts of by-products and low yields of a target compound. 17 Masked enediyne 1 was prepared by the low temperature selective mono-addition of the dichlorocarbene to the 3,4benzocyclodeca-1,5-diyne (2).…”