Patent ID: 7642366

Claim:
A Compound of formula I wherein R 1 and R 2 are independently selected from the group consisting of alkyl, aryl, or cycloalkyl, said alkyl, aryl, or cycloalkyl being unsubstituted or substituted by alkyl, alkoxy, halogen, hydroxy, amino, mono- or dialkylamino, aryl, —SO 2 —R 7 , —SO 3 − , —CO—NR 8 R 8′ , carboxy, alkoxycarbonyl, trialkylsilyl, diarylalkylsilyl, dialkylarylsilyl or triarylsilyl; R 3 is selected from the group consisting of alkyl, cycloalkyl, and aryl; R 4′ and R 4 are independently selected from the group consisting of hydrogen, alkyl and aryl; or R 4′ and R 4 together with the C-atom they are attached to form a 3-8-membered carbocyclic ring; the dotted line is absent or is present and forms a double bond; R 5 and R 6 are independently selected from the group consisting of hydrogen, alkyl and aryl; R 7 is selected from the group consisting of alkyl, aryl and NR 8 R 8′ ; and R 8 and R 8′ are independently selected from the group consisting of hydrogen, alkyl and aryl.