Boron complexation strategy for use in manipulating 1-acyldipyrromethanes
A method of making a metal complex comprises combining a 1-monoacyldipyrromethane with a compound of the formula R 1 R 2 MX, wherein M is boron, R 1 and R 2 are each independently organic substituents; and X is an anion leaving group; to produce a metal complex of the formula DMR 1 R 2 wherein DH is a 1-monoacyldipyrromethane. The methods and complexes are useful for the purification and synthesis of dipyrromethanes and porphyrins.
1. A method of making a 1,9-diacyldipyrromethane metal complex, comprising:
providing a 1-monoacyldipyrromethane-boron complex, then
acylating said 1-monoacyldipyrromethane in said complex at the 9 position to produce said 1,9-diacyldipyrromethane metal complex;
wherein said 1-monoacyldipyrromethane-boron complex is a compound of the formula DMR 1 R 2 , wherein:
D is a 1-monoacyldipyrromethane,
M is boron, and
R 1 and R 2 are each independently selected from the group consisting of alkyl, alkenyl, alkynyl, and aryl, each of which can be unsubstituted or substituted one or more times with a substituent selected from the group consisting of alkyl, alkenyl, alkynyl, aryl, alkoxy, alkylcarbonyl, alkylcarbonyloxy, alkylsulfinyl, alkylsulfonyl, alkylthio, halo, cyano, nitro, sulfo, oxo, formyl, azido, and carbamoyl.
2. The method of claim 1 , wherein said acylating step is carried out with an acylating agent in the presence of a Grignard reagent, and optionally a base, to produce said 1,9-diacyldipyrromethane metal complex.
3. The method of claim 1 , wherein said acylating step is carried out with an acid halide acylating agent in the presence of a Grignard reagent, and optionally a base, to produce said 1,9-diacyldipyrromethane metal complex.
4. The method of claim 1 , wherein said acylating step is carried out with an active ester acylating agent in the presence of a Grignard reagent, and optionally a base, to produce said 1,9-diacyldipyrromethane metal complex.
5. The method of claim 1 , wherein said acylating step is carried out with a pyridyl thioate Mukaiyama reagent in the presence of a Grignard reagent, and optionally a base, to produce said 1,9-diacyldipyrromethane metal complex.
6. The method of claim 2 , wherein the conjugate acid of said base has a pK a greater than that of the conjugate acid of the nonacylated pyrrole group in said 1-monoacyldipyrromethane.
7. The method of claim 2 , wherein said base is the deprotonated form of a compound selected from the group consisting of tetraalkylpiperidine, dicycloalkylamine, and disilazane.
8. The method of claim 2 , wherein said base is present and added as a preformed base.
9. The method of claim 2 , wherein said base is formed in situ, and wherein the conjugate acid of said base has a pK a less than that of the conjugate acid of said Grignard reagent.
10. The method of claim 2 , wherein said base is present or absent, and wherein said Grignard reagent is a hindered Grignard reagent.
11. The method of claim 1 , further comprising the step of:
decomplexing said 1,9-diacyldipyrromethane from said metal complex by combining said metal complex with an hydroxide, an alcohol, water, or combination thereof to form a product.
12. The method of claim 11 , further comprising the steps of:
combining said product with a compound of the formula R 1 R 2 M′X′ 2 in the presence of a base, where M′ is Sn, Si, Ge, or Pb, and X′ is halo, OAc, acac or OTf, to form a metal complex of the formula DM′R 1 R 2 in said mixed reaction product, wherein is said 1,9-diacyldipyrromethane; and then
separating said metal complex from said mixed reaction product.
13. The method of claim 1 , further comprising the steps of:
reducing said metal complex with a reducing agent to form a diol from said 1,9-diacyldipyrromethane; and then
condensing said diol with a dipyrromethane to form a porphyrin ring compound therefrom.
14. The method of claim 13 , wherein said reducing agent is NaBH 4 .