Preparation of Anilineboronic acids and derivatives thereof
View Patent ↗A process for preparing anilineboronic acid derivative of the formula I, by converting an aniline to a diprotected aniline by introducing two protecting groups, metalating the diprotected aniline with a metalating agent and simultaneously or subsequently reacting with a boronic ester B(OR 1,2,3 ) 3 to form a protected anilineboronic ester, which is converted, by detaching the protecting groups, to the anilineboronic esters of the formula (I).
1. A process for preparing an anilineboronic acid derivative of the formula I
comprising the steps of:
step 1: converting an aniline (II) to a diprotected aniline (III) by introducing two protecting groups PG,
step 2: metalating the diprotected aniline (III) with a metalating agent and simultaneously or subsequently reacting with a boronic ester B(OR 1,2,3 ) 3 (IV) to a protected anilineboronic ester of the formula (V), and
step 3: detaching the protecting groups PG, to form the anilineboronic ester of the formula (I)
Step 1: Protection of the aniline by dibenzylation
Step 2: Metalation of the protected aniline, conversion to boronic acid derivative
Step 3: Detachment of the protecting group
where
R is H, F, Cl, Br, I, a branched or unbranched, substituted or unsubstituted C 1 –C 20 —, a substituted or unsubstituted C 6 –C 12 -aryl or -aryloxy radical, a heteroaryl radical, a heteroaryloxy radical, a substituted or unsubstituted C 3 –C 8 -cycloalkyl radical, a dialkyl group, a diarylamino group, an alkyl group, an arylthio group, an ester group or acetal group;
X is H, Cl, Br, I or F;
R 1 , R 2 , R 3 are each independently H, a branched or unbranched, substituted or unsubstituted C 1 –C 20 -alkyl group, and two R 1-3 radicals together may optionally form a ring, or are each further B(OR 1,2,3 ) 3 radicals.
2. The process as claimed in claim 1 , wherein the protecting groups PG are substituted or unsubstituted benzyl groups and step 1 further comprises alkylating the aniline (II) nitrogen atom with an alkylating agent.
3. The process as claimed in claim 1 , wherein the protecting groups PG are substituted or unsubstituted benzyl groups and wherein step 1 further comprises reductively aminating a substituted or unsubstituted benzaldehyde with the aniline (II) in the presence of a hydride donor.
4. The process as claimed in claim 1 , wherein the protecting groups PG are carbamoyl or acyl groups bearing organic substituted or unsubstituted radicals and wherein step 1 further comprises acylating the aniline (II) nitrogen atom with at least one reactive carboxylic acid derivative.
5. The process as claimed in claim 1 , wherein the protecting groups are triorganosilyl groups and wherein step 1 further comprises reacting the aniline (II) with an electrophilic silylating agent.
6. The process as claimed In claim 1 , wherein step 3 further comprises hydrogenolysis in a hydrogenous atmosphere in the presence of a transition metal catalyst under a pressure of from 0.5 to 400 bar.
7. The process as claimed in claim 1 , wherein step 3 further comprises transfer hydrogenation in the presence of a transition metal catalyst and one of a hydride donor, a Brønsted or Lewis acid or Brønsted base.
8. The process as claimed in claim 1 , wherein step 2 further comprises reading the diprotected aniline (III) with an organomagnesium or organolithium compound.
9. The process as claimed in claim 1 , wherein step 2 further comprises reacting the diprotected aniline (III) with a reactive metal selected from the group consisting of: alkali metals, alkaline earth metals and zinc.
10. The process as claimed in claim 1 , wherein step 2 is carried out in at least one solvent selected from the group consisting of: triethylamine, diethyl ether, di-n-propyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, tert-butyl methyl ether, benzene, toluene, xylene, anisole, pentane, hexane, isohexane, heptane, petroleum ether (alkane mixtures), cyclohexane, and methylcyclohexane.
11. The process as claimed in claim 1 , wherein step 2 further comprises initially charging the metalating agent in a solvent, and subsequently metering in the diprotected aniline (III) into the metalating agent and solvent to form a reaction mixture, and subsequently reacting the boronic ester B(OR 1,2,3 ) 3 (IV) with the reaction mixture.
12. The process as claimed in claim 1 , wherein step 2 further comprises initially charging the metalating agent in a solvent and the diprotected aniline (III) and the boronic ester B(OR 1,2,3 ) 3 (IV) are metered in to the metalating agent and solvent in parallel or as a mixture.
13. The process as claimed in claim 1 , wherein step 2 further comprises initially charging the diprotected aniline (III) in a first solvent and then the metalating agent and a second solvent is metered in to the diprotected aniline (III) and first solvent to form a reaction mixture, and reacting the boronic ester B(OR 1,2,3 ) 3 (IV) with the reaction mixture.
14. The process as claimed in claim 1 , wherein step 2 further comprises initially charging the diprotected aniline (III) and the boronic ester B(OR 1,2,3 ) 3 in a solvent to form a reaction mixture (IV) and metering in the metalating agent into the reaction mixture.
15. The process as claimed in claim 1 , wherein step 2 further comprises reacting the diprotected aniline (III) with a reactive metal in a solvent.
16. The process as claimed in claim 1 , wherein step 2 further comprises reacting the diprotected aniline (III) and the boronic ester B(OR 1,2,3 ) 3 (IV) with a reactive metal selected from the group consisting of: alkali metals, alkaline earth metals, and zinc.
17. The process as claimed in claim 1 carried out at a temperature in the range from −100 to 120° C.
18. The process as claimed in claim 1 , wherein the metalating agent is a Grignard compound and step 2 is carried out in the range from 0 to 40° C.
19. The process as claimed in claim 2 , wherein step 1 further comprises alkylating the aniline nitrogen atom with an alkylating agent and at least one of a base or a catalyst.
20. The process as claimed in claim 4 , wherein step 1 further comprises acylating the aniline (II) nitrogen atom with at least one reactive carboxylic acid derivative in the presence of at least one of acylation catalyst, base or alkali metal.
21. The process as claimed in claim 5 , wherein step 1 further comprises reacting the aniline (II) with an electrophilic silylating agent in the presence of a base or an alkali derivative.
22. The process as claimed in claim 9 , wherein step 2 further comprises using a redox catalyst.
23. The process as claimed in claim 15 , wherein step 2 further comprises using a redox catalyst.
24. The process as claimed in claim 16 , wherein step further comprises using a redox catalyst.
25. The process as claimed in claim 11 , wherein the boronic ester B(OR 1,2,3 ) 3 (IV) is mixed with a solvent prior to reaction with the reaction mixture.
26. The process as claimed in claim 1 , wherein the metalating agent is an organolithium compound and step 2 is carried out at a temperature in the range from −100° C. to 30° C.