Process for synthesis of indenes

A process for forming a compound of formula II

• wherein
• R1, R2 are each (1-10C)alkyl;
• and
• L is a bridging group of the formula —[C(RxRy)]n— wherein n is 1, 2 or 3 and Rx and Ry are each independently hydrogen, (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl or (1-6C)alkoxy;
• or a group —SiRaRb wherein Ra and Rb are each independently selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy or phenyl;
• wherein the process comprises:
• (i) forming a compound of formula I by a process comprising the steps of:
• (a) reacting a compound of formula A:
• wherein R1 and R2 are each as defined above;
• with a chlorinating or brominating agent to form a compound of formula B:
• wherein R1 and R2 are each as defined above and X is chloro or bromo;
• and adding 1,2,3,4-tetramethylbenzene and a Lewis acid catalyst to the reaction mixture to react with compound B to form a compound of formula C:
• wherein R1 and R2 are each as defined above;
• (b) reacting the compound of formula C with a solution of a hydride transfer reagent followed by adding a dehydrating agent to the reaction mixture to form a compound of formula I shown below:
• wherein R1 and R2 are each as defined above;
• (ii) reacting the compound of formula I with an organolithium, organosodium or organopotassium compound of the formula:
• MQ
• wherein M is lithium, sodium, or potassium and Q is an (1-6C)alkyl or aryl group;
• to form a compound of formula D shown below:
• (iii) reacting two equivalents of a compound of formula D shown above with one equivalent of a compound having formula E shown below:
• Z1-L-Z2 (E)
• wherein L is as defined above and Z1 and Z2 are leaving groups to form a compound of formula II.

A process for forming a compound of formula III

• wherein
• R1 and R2 are each (1-10C)alkyl;
• L is a bridging group of the formula —[C(RxRy)]n— wherein n is 1, 2 or 3 and Rx and Ry are each independently hydrogen, (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl or (1-6C)alkoxy;
• or a group —SiRaRb wherein Ra and Rb are each independently selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy or phenyl;
• X is zirconium, hafnium or titanium;
• Y is selected from halo, hydride, a phosphonated or sulfonated anion, or a (1-6C)alkyl, (1-6C)alkoxy, aryl or aryloxy group which is optionally substituted with halo, nitro, amino, phenyl, (1-6C)alkoxy, or Si[(1-4C)alkyl]3,
• wherein the process comprises:
• (i) forming a compound of formula II by a process comprising the steps of:
• (a) reacting a compound of formula A:
• wherein R1 and R2 are each as defined above;
• with a chlorinating or brominating agent to form a compound of formula B:
• wherein R1 and R2 are each as defined above and X is chloro or bromo;
• and adding 1,2,3,4-tetramethylbenzene and a Lewis acid catalyst to the reaction mixture to react with compound B to form a compound of formula C:
• wherein R1 and R2 are each as defined above:
• (b) reacting the compound of formula C with a solution of a hydride transfer reagent followed by adding a dehydrating agent to the reaction mixture to form a compound of formula I shown below:
• wherein R1 and R2 are each as defined above;
• (c) reacting the compound of formula I with an organolithium, organosodium or organopotassium compound of the formula:
• MQ
• wherein M is lithium, sodium, or potassium and Q is an (1-6C)alkyl or aryl group;
• to form a compound of formula D shown below:
• (d) reacting two equivalents of a compound of formula D shown above with one equivalent of a compound having formula E shown below:
• Z1-L-Z2 (E)
• wherein L is as defined above and Z1 and Z2 are leaving groups to form a compound of formula II shown below:
• (ii) reacting the compound of formula II, or a salt thereof, with a compound of the formula:
• X(Y)2(Z3)2
• wherein X and Y are as defined above and Z3 is a leaving group.