Methods for forming protected organoboronic acids
Described are methods of forming protected boronic acids that provide in a manner that is straightforward, scalable, and cost-effective a wide variety of building blocks, such as building blocks containing complex and/or pharmaceutically important structures, and/or provide simple or complex protected organoboronic acid building blocks. A first method includes reacting an imino-di-carboxylic acid and an organoboronate salt. A second method includes reacting a N-substituted morpholine dione and an organoboronic acid.
1. A method of forming a protected boronic acid, comprising:
reacting in a reaction mixture
an imino-di-carboxylic acid, and
an organoboronate salt represented by formula (I):
[R 1 —B(OR 2 )(OR 3 )(OR 4 )] − M + (I);
wherein
R 1 is an organic group,
R 2 , R 3 and R 4 independently are selected from the group consisting of an alkyl group and an aryl group, and
M + is selected from the group consisting of a metal ion, a metal halide ion and an ammonium ion; and
the reaction mixture further comprises a polar aprotic solvent;
wherein the reacting comprises maintaining the reaction mixture at a temperature of at least 100° C.; and
thereby forming a protected organoboronic acid represented by formula (III) in the reaction mixture:
wherein R 10 , R 11 , R 12 , R 13 and R 14 independently are selected from the group consisting of a hydrogen group and an organic group.
2. The method of claim 1 , wherein R 1 is an alkyl group, a heteroalkyl group, an alkenyl group, a heteroalkenyl group, an alkynyl group, a heteroalkynyl group, an aryl group, a heteroaryl group, or a combination of at least two of these groups.
3. The method of claim 1 , wherein R 1 is represented by formula (IV):
Y—R 5 —(R 6 ) m — (IV),
wherein
Y is a halogen group or a pseudohalogen group;
R 5 is an aryl group or a heteroaryl group;
R 6 is an alkyl group, a heteroalkyl group, an alkenyl group, a heteroalkenyl group, an alkynyl group, a heteroalkynyl group, an aryl group, a heteroaryl group, or a combination of at least two of these groups; and
m is 0 or 1.
4. The method of claim 3 , wherein R 5 is a heteroaryl group.
5. The method of claim 1 , wherein R 1 is a heterocyclic group, an alkynyl group or an alkenyl group.
6. The method of claim 5 , wherein said heterocyclic group is selected from the group consisting of pyridine, indole, isoindole, indazole, purine, indolizidine, quinoline, isoquinoline, quinazoline, pteridine, quinolizidine, pyrrole, pyrazine, pyridazine, pyrimidine, imidazole, pyrasole, isoxazole, oxazole, thiazole, benzthiazole, furan, benzofuran, thiophene and benzothiophene.
7. The method of claim 1 , wherein R 1 is a 2-heterocyclic group selected from the group consisting of 2-pyridyl, 2-indolyl, 2-isoindolyl, 2-indazolyl, 2-purinyl, 2-indolizidinyl, 2-quinolinyl, 2-isoquinolinyl, 2-quinazolinyl, 2-pteridinyl, 2-quinolizidinyl, 2-pyrrolyl, 2-pyrazinyl, 2-pyridazinyl, 2-pyrimidinyl, 2-imidazolyl, 2-pyrasolyl, 2-isoxazolyl, 2-oxazolyl, 2-thiazolyl, 2-benzthiazolyl, 2-furyl, 2-benzofuryl, 2-thiophenyl, and 2-benzthiophenyl.
8. The method of claim 1 , wherein R 2 , R 3 and R 4 are each independently an alkyl group containing from 1 to 4 carbon atoms.
9. The method of claim 8 , wherein said alkyl group is methyl (—CH 3 ) or isopropyl (—CH(CH 3 ) 2 ).
10. The method of claim 1 , wherein M + is selected from the group consisting of Li + , Na + , K + , MgX + , CaX + ,Zn + , Bu 4 N + , and Me 4 N + ; and X is F, Cl, Br or I.
11. The method of claim 10 , wherein M + is Li + or MgX + .
12. The method of claim 1 , wherein R 10 is methyl, and each of R 11 , R 12 , R 13 and R 14 is hydrogen.
13. The method of claim 1 , wherein the polar aprotic solvent is selected from the group consisting of tetrahydrofuran (THF), dioxane, dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), toluene and xylene.
14. The method of claim 1 , wherein the polar aprotic solvent is DMSO.
15. The method of claim 1 , wherein the reaction mixture is at a temperature of from 100° C. to 200° C.
16. The method of claim 1 , further comprising:
reacting in a reaction mixture
an organohalide or an organo-pseudohalide (V), an organolithium reagent, and a boronate ester, to form the organoboronate salt (VI), as represented by the following reaction scheme:
wherein Y is a halogen or a pseudohalogen; and R 7 is a hydrocarbon group.
17. The method of claim 1 , further comprising:
reacting in a reaction mixture
an organic compound (VII), and
a first organolithium reagent to form a second organolithium reagent (VIII); and
reacting in a reaction mixture said second organolithium reagent (VIII), and
a boronate ester to form a organoboronate salt (VI), as represented by the following reaction scheme:
wherein R 7 is a hydrocarbon group.
18. The method of claim 1 , further comprising:
reacting in a reaction mixture
an organic compound (VII), and MgCl/LiCl 2,2,6,6-tetramethylpiperidyl amide to form a Grignard reagent (IX); and
reacting in a reaction mixture said Grignard reagent (IX) and a boronate ester to form a organoboronate salt (X), as represented by the following reaction scheme: