ChemInform Abstract: Reaction of Vinylidenecyclopropane with Simmons‐Smith Reagent Activated by Ultrasound.

Abstract

Under ultrasound the reaction between vinylidenecyclopropane (I) and Simmons‐Smith reagent (II) affords the expected products (III) and (IV) along with the cyclobutene (V).

The Chemistry of Highly Strained Oligospirocyclopropane Systems

“…11a,101-104 Surprisingly, the application of ultrasound in the case of allene 64 only complicated the situation in that it led to the formation of the 1-iodocyclobutene derivative 65 (Scheme 8). 105 The authors rationalize this as resulting from the addition of an ethoxyethyl radical to the allene 64 followed by radical ring expansion of a new type and subsequent trapping of an iodine atom. It was found, however, that the yields of biscyclopropanated products from allenes of type 64 in Simmons-Smith cyclopropanations can be substantially improved using diiodomethane/trimethylaluminum as a reagent.…”

“…One more reaction to be mentioned in this context is the cyclopropanation of ethenylidenecyclopropanes such as 64 and related allenes with the Simmons−Smith reagent. Normally it provides mixtures of mono- and dicyclopropanated products such as 5 and 12 in low to moderate yields. 11a,− Surprisingly, the application of ultrasound in the case of allene 64 only complicated the situation in that it led to the formation of the 1-iodocyclobutene derivative 65 (Scheme ) . The authors rationalize this as resulting from the addition of an ethoxyethyl radical to the allene 64 followed by radical ring expansion of a new type and subsequent trapping of an iodine atom.…”

The First Enantiomerically Pure Triangulane (M)-Trispiro[2.0.0.2.1.1]nonane Is a σ-[4]Helicene

“…Structure of (R,R)-6 a in the crystal. The enantiomerically pure acid (R)-3 was first transformed to its ethyl ester ((R)-7), [12,17] following a standard procedure, [18] which was then cyclopropanated with the Simmons ± Smith reagent (CH 2 I 2 /Zn) [19] accelerated by ultrasonication [20] to give a mixture of ethyl endo-(1R,3R)-and exo-(1R,3S)-…”

Das erste enantiomerenreine Triangulan: (M)-Trispiro[2.0.0.2.1.1]nonan ist ein σ-[4]Helicen

“…4 b [13] mit Dehydroabietylamin (DAA) durchgeführt (Schema 1). Zwei Kristallisationen aus Ethanol und anschlieûende Umsetzung mit wäûrigem Natriumhydroxid sowie Ansäuern mit konzentrierter Salzsäure lieferten enantiomerenreines (R)-(À)-3 ([a] 20 D À 183.7, c 1.00 in CHCl 3 , ee 100 %) und (S)-()-3 ([a] 20 D 183.2, c 1.00 in CHCl 3 , ee 100 %).…”

“…Struktur von (R,R)-6a im Kristall. [16] Die enantiomerenreine Säure (R)-3 wurde zunächst nach einem Standardverfahren [18] in den Ethylester (R)-7 [12,17] überführt, und dieser wurde dann mit dem Simmons-Smith-Reagens (CH 2 I 2 /Zn), [19] beschleunigt durch Ultraschallbehandlung, [20] cyclopropaniert, und man erhielt eine Mischung 21] Diese Diastereomere lieûen sich leicht durch Säulenchromatographie trennen und wurden in 28 bzw. 41 % Ausbeute isoliert (Schema 2).…”