Generation and Trapping of Cyclopropenes from 2‐Alkoxy‐1,1‐dichlorocyclopropanes

Abstract

In presence of crown ether, 2‐alkoxy‐1,1‐dichlorocyclopropanes react with t‐BuOK/THF preferentially via ring opening to 2‐chloroalk‐2‐en‐1‐ones and alkynones or to chlorocyclopropenes. The latter may be intercepted with 1,3‐diphenylisobenzofuran, but in the absence of trapping agent, the rearrangement to vinylcarbenes does not occur.

Thermally Induced Cyclopropene−Carbene Rearrangements: An Overview

“…It is interesting to note that 3-ethoxy-1-chlorocyclopropene 82 , generated by the halodesilylation of 1,1-dichloro-2-trimethylsilyl-3-ethoxycyclopropane, is trapped in situ by diphenylisobenzofuran, though when 82 is generated by dehydrochlorination of the dichloride with KO- t -Bu in tetrahydrofuran in the presence of the furan, a most unusual allene, 83 , is isolated:

…”

(Trimethylsilyl)ethoxyacetylene as a Dehydrating Agent for Polyanhydride Synthesis

“…c. Synthesis of (Trimethylsilyl)ethoxyacetylene (TMSEA). TMSEA was synthesized according to a literature reported methods. − Briefly, ethoxyacetylene solution (75.26 g, 0.54 mol of ethoxyacetylene) was dissolved in 1000 mL of anhydrous ethyl ether at 0 °C. Then methyllithium solution (331.6 mL, 242.73 g, 0.56 mol) was added dropwise in 1 h, and the mixture was stirred at 0 °C for another 30 min.…”

Studies Directed toward the Total Synthesis of Lactonamycin: Control of the Sense of Cycloaddition of a Quinone through Directed Intramolecular Catalysis

“…Hydrogenolysis of the two benzyl esters gave rise to a diacid. However, dehydration with trimethylsilylethoxyacetylene11 only produced trace amounts of the desired homophthalic anhydride 24 , presumably as a result of solubility issues. It is possible that the difficulties in the cycloaddition reaction of 21 and 22 reflect the usual complexities associated with Diels–Alder reactions of 1,1‐disubstituted dienes, in which the required 2,3‐ s‐cis coplanar conformer may be of high energy.…”