Anwendung der α-Alkinon-Cyclisierung: Totalsynthese von (±)-Alben

Application of the α-Alkynone Cyclization: Total Synthesis of (±)-Albene A synthesis of the racemic form of the natural tricyclic hydrocarbon albene (1) from the Diels-Alder adduct 2 of tiglyl chloride and cyclopentadiene is described (24% yield). The key step 5→6 involves a thermal α-alkynone cyclization (Scheme 3), which is able to establish a new quarternary C-atom at an unactivated position with a high degree of regiospecificity.     

Formale Totalsynthese von (±)-Isocomen durch Anwendung der α-Alkinon-Cyclisierung

Formal Total Synthesis of (±)-Isocomen by Application of the α-Alkinon Cyclization A total synthesis of the racemic form of the sesquiterpene isocomene ( A ) was accomplished by application of the cyclopentenone anellation B→D (Scheme 1) which includes the α-alkynone cyclization C→D , a gas-phase flow thermolytic process. Starting with the known product 2 (Scheme 3) of the anellation B→D , the elaboration of ring C of A proceeded in 9 steps to the α-alkynone 16 (Scheme 5) which was cyclized at 540° selectively to give the angularly fused triquinane 4 (77%). A two-step procedure then led to 5 (Scheme 6), a last but one intermediate in a known total synthesis of (±)- A . The conversion of 16 to 4 also demonstrated the compatibility of an acetoxy function with the anellation sequence B→D .     

Eine einfache und flexible Synthese von Pyrrolen aus α,β-ungesättigten Sulfonen

A Simple and Flexible Synthesis of Pyrroles from α , β -Unsaturated Sulfones: The addition of alkyl isocyanoacetates and isocyanoacetonitrile to α,β-unsaturated sulfones affords a convenient and broad access to pyrroles with unusual substitution patterns (see Scheme 2). The α,β-unsaturated sulfones required as starting materials are easily obtained from different olefines.