The Synthetic Routes of 9-Phenyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole

The Synthetic Routes of 9-Phenyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole: A Comprehensive Overview in the Chemical Industry

9-Phenyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, commonly referred to as PMTB, is an important synthetic intermediate in the chemical industry.
Since its discovery, numerous synthetic routes have been reported in the literature for the production of PMTB.
In this article, we will provide a comprehensive overview of the existing synthetic routes for PMTB, their advantages and limitations, and the latest developments in this field.

1. Hydroboration-oxidation of phenylboronic acid

The traditional synthetic route for PMTB involves the hydroboration-oxidation of phenylboronic acid.
This route involves the reduction of boron trifluoride ether (BF3) with lithium aluminum hydride (LiAlH4) to form a borane, which is then reacted with phenylboric acid to form PMTB.
This method is relatively simple and cost-effective, but it requires the handling of dangerous reagents such as BF3 and LiAlH4.

2. Palladium-catalyzed cross-coupling

Another method for the synthesis of PMTB is palladium-catalyzed cross-coupling.
In this method, a Grignard reagent is synthesized from phenylmagnesium bromide (PhMgBr) and treated with tetrakis(t-butylphenyl)borate (TBPB) to form a phenylborane intermediate.
This intermediate is then coupled with 2-dioxaborolane (DOB) in the presence of a palladium catalyst to form PMTB.
This method is more efficient and less dangerous than the hydroboration-oxidation method, but it requires the use of expensive and limited supply of palladium catalysts.

3. nickel-catalyzed cross-coupling

A newer method for the synthesis of PMTB is nickel-catalyzed cross-coupling.
In this method, a boronic acid is treated with a primary or secondary amine to form an amide, which is then treated with a Grignard reagent to form a phosphine intermediate.
This intermediate is then reacted with a second Grignard reagent in the presence of a nickel catalyst to form PMTB.
This method is more efficient and less expensive than the palladium-catalyzed method, and it does not require the use of expensive and limited supply of palladium catalysts.

4. Photoredox-catalyzed process

A recent method for the synthesis of PMTB is the photoredox-catalyzed process.
In this method, phenylboronic acid is treated with a photoredox catalyst in the presence of a sacrificial redox couple to form PMTB.
This method is more environmentally friendly and less hazardous than the traditional methods, as it does not require the use of dangerous reagents.

Advantages and limitations:

The advantages of the above-mentioned synthetic routes for PMTB include relatively simple reaction conditions, good yield, and a wide range of applications in organic synthesis and materials science.
However, each method also has its own limitations.
For example, the hydroboration-oxidation method requires the handling of dangerous reagents, the palladium-catalyzed method is expensive, the nickel-catalyzed method requires specialized equipment, and the photoredox-catalyzed process may be less efficient.

Future developments:

The synthetic routes for PMTB are constantly evolving, and several recent studies have reported new and improved methods for