Methods for preparing formaldehyde from carbon dioxide
The present disclosure provides, inter alia, methods for preparing formaldehyde from carbon dioxide using bis(silyl)acetals, methods for incorporating carbon derived from carbon dioxide into a complex organic molecule derived from formaldehyde using bis(silyl)acetals, and methods for generating an isotopologue of a complex organic molecule derived from formaldehyde using bis(silyl)acetals.
1. A method for preparing formaldehyde, comprising the steps of:
(a) obtaining a bis(silyl)acetal; and
(b) generating formaldehyde by any one of the following:
adding a fluoride compound to a solution of the bis(silyl)acetal in a solvent; or
(ii) reacting the bis(silyl)acetal with water in a solvent; or
(iii) reacting the bis(silyl)acetal with an acid in a solvent.
2. The method of claim 1 , wherein the bis(silyl)acetal is generated by the reaction between carbon dioxide and a silane in the presence of a compound prepared from a multidentate ligand having the structure of:
and B(C 6 F 5 ) 3 ,
wherein the silane is R 3 SiH and R is selected from H, alkyl and aryl.
3. The method of claim 1 , wherein the bis(silyl)acetal is H 2 C(OSiPh 3 ) 2 .
4. The method of claim 1 , wherein the formaldehyde generated is anhydrous.
5. The method of claim 1 , wherein the fluoride compound is selected from CsF, KF, NaF, LiF, tetra(n-butyl)ammonium fluoride, and trimethyltin fluoride.
6. The method of claim 1 , wherein the fluoride compound is CsF.
7. The method of claim 1 , wherein the solvent in each of step (b)(i), step (b)(ii) and step (b)(iii) is independently selected from acetonitrile, acetone, DMF, DMSO, γ-Butyrolactone, ethers, aromatic solvents and aliphatic solvents.
8. The method of claim 1 , wherein the solvent in step (b)(i) is acetonitrile, the solvent in step (b)(ii) is DMSO, and the solvent in step (b)(iii) is acetonitrile.
9. The method of claim 1 , wherein the acid is selected from sulfuric acid, nitric acid, hydrohalic acids, carboxylic acid and phosphoric acid.
10. The method of claim 1 , wherein the acid is sulfuric acid.
11. A method for completing a transformation that involves formaldehyde, comprising substituting formaldehyde with a bis(silyl)acetal.
12. The method of claim 11 , wherein the bis(silyl)acetal is generated by the reaction between carbon dioxide and a silane in the presence of a compound prepared from a multidentate ligand having the structure of:
and B(C 6 F 5 ) 3 ,
wherein the silane is R 3 SiH and R is selected from H, alkyl and aryl.
13. The method of claim 11 , wherein the bis(silyl)acetal is H 2 C(OSiPh 3 ) 2 .
14. The method of claim 11 , wherein the transformation is selected from: the formation of a terminal olefin in a Wittig reaction, the synthesis of hexamine from ammonia, the Pictet Spengler reaction for the preparation of heterocycles, and the synthesis of benzazoles.
15. A method for incorporating carbon derived from carbon dioxide into a complex organic molecule derived from formaldehyde, comprising the steps of:
(a) obtaining a bis(silyl)acetal by the reaction between carbon dioxide and a silane in the presence of a compound prepared from a multidentate ligand having the structure of:
and B(C 6 F 5 ) 3 , wherein the silane is R 3 SiH and R is selected from H, alkyl and aryl; and
(b) substituting formaldehyde with the bis(silyl)acetal in a reaction that generates the complex organic molecule.
16. The method of claim 15 , wherein the bis(silyl)acetal is H 2 C(OSiPh 3 ) 2 .
17. The method of claim 15 , wherein the reaction is selected from:
the formation of a terminal olefin in a Wittig reaction, the synthesis of hexamine from ammonia, the Pictet Spengler reaction for the preparation of heterocycles, and the synthesis of benzazoles.
18. The method of claim 15 , wherein the bis(silyl)acetal generated in step (a) is isotope-labeled by using isotope-labeled carbon dioxide and/or isotope-labeled silane in the reaction mixture.
19. The method of claim 18 , wherein the carbon dioxide is isotope-labeled using 11 C, 13 C, or 14 C.
20. The method of claim 18 , wherein the silane is isotope-labeled using 2 H or 3 H.
21. The method of claim 15 , wherein the bis(silyl)acetal generated in step (a) is isotope-labeled by using 13 C-labeled carbon dioxide and/or 2 H-labeled silane in the reaction mixture.
22. A method for generating an isotopologue of a complex organic molecule derived from formaldehyde, comprising the steps of:
(a) generating isotope-labeled bis(silyl)acetal according to the method of claim 2 by using isotope-labeled carbon dioxide and/or isotope-labeled silane in the reaction mixture; and
(b) generating the isotopologue of the complex organic molecule by using the isotope-labeled bis(silyl)acetal obtained in step (a).
23. The method of claim 22 , wherein the carbon dioxide is isotope-labeled using 11 C, 13 C, or 14 C.
24. The method of claim 22 , wherein the silane is isotope-labeled using 2 H or 3 H.
25. The method of claim 22 , wherein the bis(silyl)acetal generated in step (a) is isotope-labeled by using 13 C-labeled carbon dioxide and/or 2 H-labeled silane in the reaction mixture.
26. The method of claim 22 , wherein the isotopologue generated is a probe for positron emission tomography (PET).
27. The method of claim 26 , wherein the probe for PET is selected from the group consisting of [ 11 C] Acetate, [ 11 C] 25B-NBOMe (Cimbi-36), [ 11 C] Carfentanil, [ 11 C] DASB, [ 11 C] DTBZ, [ 11 C] ME@HAPTHI, [ 11 C] Pittsburgh compound B, [ 11 C] Raclopride, [ 11 C] Verapamil, [ 11 C] N-Methylspiperone, [ 11 C] Martinostat, [ 11 C] Methionine, [ 11 C] choline, and combinations thereof.
28. A method for carrying out a chemical reaction with a formaldehyde surrogate comprising replacing formaldehyde in the chemical reaction with a bis(silyl)acetal.
29. The method of claim 28 , wherein the bis(silyl)acetal is H 2 C(OSiPh 3 ) 2 .
30. The method of claim 28 , wherein the chemical reaction involves formation of bonds selected from C—C, C—N, C—O and C—S, the formation of heterocycles, and combinations thereof.