The Synthetic Routes of 9,9'-Spirobi[9H-fluorene]-4-ylboronicacid

9,9'-Spirobi[9H-fluorene]-4-ylboronicacid is an important building block in organic synthesis and has a wide range of applications in the chemical industry.
This molecule can be synthesized through several different routes, each with its own advantages and disadvantages.
In this article, we will discuss three of the most commonly used synthetic routes for the preparation of 9,9'-spirobi[9H-fluorene]-4-ylboronicacid.

Route 1: via an enolate intermediate

The first synthetic route for the preparation of 9,9'-spirobi[9H-fluorene]-4-ylboronicacid involves the use of an enolate intermediate.
This route is shown below:

1. To a suspension of 9,9'-spirobi[9H-fluorene]-4,4'-dicarboxylic acid (1) in dichloromethane, a solution of diboronic acid (2) and triphenylphosphine (3) in toluene is added.
   
2. The reaction mixture is stirred for 12 hours at room temperature and then at 60-70°C for 8 hours.
   
3. The reaction mixture is cooled to room temperature and then quenched with aqueous sodium bicarbonate, followed by extraction with ethyl acetate.
   
4. The organic layer is dried over anhydrous sodium sulfate, filtered and the solvent is removed under vacuum.
   
5. The residue is purified by flash chromatography using a mixture of ethyl acetate and petroleum ether as the eluent.
   

Route 2: via a boronate ester intermediate

The second synthetic route for the preparation of 9,9'-spirobi[9H-fluorene]-4-ylboronicacid involves the use of a boronate ester intermediate.
This route is shown below:

1. To a suspension of 9,9'-spirobi[9H-fluorene]-4,4'-dicarboxylic acid (1) in dry dichloromethane, a solution of n-butylboronic acid (2) in dichloromethane is added.
   
2. The reaction mixture is stirred for 12 hours at room temperature and then at 60-70°C for 8 hours.
   
3. The reaction mixture is cooled to room temperature and then quenched with aqueous sodium bicarbonate, followed by extraction with ethyl acetate.
   
4. The organic layer is dried over anhydrous sodium sulfate, filtered and the solvent is removed under vacuum.
   
5. The residue is purified by flash chromatography using a mixture of ethyl acetate and petroleum ether as the eluent.
   

Route 3: via a boronic acid intermediate

The third synthetic route for the preparation of 9,9'-spirobi[9H-fluorene]-4-ylboronicacid involves the use of a boronic acid intermediate.
This route is shown below:

1. To a suspension of 9,9'-spirobi[9H-fluorene]-4,4'-dicarboxylic acid (1) in dichloromethane, a solution of diboronic acid (2) in dichloromethane is added.
   
2. The reaction mixture is stirred for 12 hours at room temperature and then at 60-70°C for 8 hours.
   
3. The reaction mixture is cooled to room temperature and then quenched with aqueous sodium bicarbonate, followed by extraction with ethyl acetate.
   
4. The organic layer is dried over anhydrous sodium sulf