Formation of tetra-substituted enamides and stereoselective reduction thereof
View Patent ↗The present invention is directed to a practical process for the preparation of an enamide (II) by palladium catalyzed coupling of a primary amide (IV) with a compound of structural formula (III), as shown below: As well as to crystalline forms of a compound produced by this process, in particular, an anhydrous crystal form, Form B, and crystalline solvates falling into three patterns, Type 1, Type 2, and Type 3, and crystalline intermediate compounds produced in the process. Still further, the present invention relates to the stereoselective reduction of the tetrasubstituted enamide (II) to the corresponding amide (I).
1. A process for the stereoselective synthesis of amide (I):
wherein:
R 1 is selected from: hydrogen, halogen, —C(O)OR e , —C(O)NR f 2 , —NR f 2 , and cyano;
R 2 is selected from: hydrogen, halogen and hydroxyl;
R 3 is
R a is:
each R c is independently selected from halogen, hydroxy, C 1-3 alkyl, cyano, methoxy and trifluoromethyl;
each R d is independently selected from: halogen, hydroxy, cyano, methoxy and trifluoromethyl;
R e is selected from: hydrogen, straight or branched chain C 1-10 alkyl, aryl-C 1-6 alkyl-, aryl, heteroaryl, wherein aryl and heteroaryl moieties are optionally substituted with one to three R c substituents, and the alkyl moiety is unsubstituted or substituted with one, two or three R d moieties; each R f is independently selected from hydrogen, straight or branched chain C 1-6 alkyl, phenyl-C 1-6 alkyl-, wherein alkyl moieties are unsubstituted or substituted with one or two R d substituents and wherein the phenyl moiety is unsubstituted or substituted with one, two or three R c substituents; comprising treating an enamide compound formula (II):
with hydrogen gas in the presence of a chiral catalyst.
2. The process according to claim 1 , wherein the chiral catalyst is selected from:
(1) a chiral catalyst formed in situ by contacting a metal precursor, a ligand and optionally an activator; and
(2) a preformed catalyst complex.
3. The process according to claim 1 wherein:
R 1 is selected from amido and cyano;
R 2 is selected from hydrogen and chlorine;
R 3 is
and R a is:
4. The process according to claim 3 wherein:
R 1 is cyano; R 2 is chlorine; R 3 is:
R a is
the chiral catalyst is selected from:
(1) a chiral catalyst formed in situ by contacting a metal precursor, a ligand and optionally an activator; wherein the metal precursor is selected from: (COD) 2 RhBF 4 , [(COD)RhCl] 2 , [(NBD)RhCl] 2 , (COD) 2 RhOTf, (NBD) 2 RhBF 4 , (NBD) 2 RhOTf, and (COD)Ru(methallyl) 2 ; the ligand is selected from: (R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-3,5-dimethylphenylphosphine, (−)-TMBTP, and (R)-Hexaphemp; and the activator is absent or tetrafluoroboric acid; and
(2) a preformed catalyst complex: (R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-3,5-dimethylphenylphosphine (COD)RhBF 4 .
5. The process according to claim 3 wherein:
R 1 is amido; R 2 is chlorine; R 3 is:
R a is
the hydrogen pressure is from 1 to 100 atmospheres,
the temperature is from ambient to 90° C.
the solvent is selected from pure or mixtures of: MeOH, EtOH, IPA, 2,2,2-trifluoroethanol, THF and 1,2-dichloroethane
the chiral catalyst is selected from:
(1) a chiral catalyst formed in situ by contacting a metal precursor, a ligand and optionally an activator; wherein the metal precursor is selected from: (COD) 2 RhBF 4 , (COD) 2 RhOTf, (NBD) 2 RhBF 4 , (NBD) 2 RhOTf, and (COD)Ru(methallyl) 2 ; the ligand is selected from: (R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine, (R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-1-napthylphosphine, (R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-3,5-dimethylphenylphosphine, (R,S)-(diphenylphosphino)ferrocenyl-ethyldi-t-butylphosphine, (−)-TMBTP, (R)-hexaphemp, (R)-xyl-BINAP, the activator is absent or tetrafluoroboric acid; or
(2) a preformed catalyst complex selected from: (−)-TMBTP(COD)RhBF 4 , (−)-TMBTP(COD)RhOTf, (−)-TMBTP(NBD)RhBF 4 , or (−)-TMBTP(NBD)RhOTf, ((R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine)(COD)RhBF 4 , ((R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine)(COD)RhOTf, ((R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine)(NBD)RhBF 4 , or ((R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine)(NBD)RhOTf additionally comprising an additive selected from: tetrafluoroboric acid, trifluoroacetic acid, BF 3 , BF 31 .IPA and BF 3 .MeOH.
6. The process according to claim 5 wherein:
R 1 is amido; R 2 is chlorine; R 3 is:
R a is
the hydrogen pressure is from 10-40 atmospheres,
the temperature is from 35 to 65° C.
the solvent is selected from pure or mixtures of: MeOH, IPA and 2,2,2-trifluoroethanol
the chiral catalyst is selected from:
(1) a chiral catalyst formed in situ by contacting a metal precursor, a ligand and optionally an activator; wherein the metal precursor is selected from:
(COD) 2 RhBF 4 , (COD) 2 RhOTf, (NBD) 2 RhBF 4 , and (NBD) 2 RhOTf, the ligand is selected from: (R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine and (−)-TMBTP, the activator is absent; or
(2) a preformed catalyst complex selected from: (−)-TMBTP(COD)RhBF 4 , ((R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine)(COD)RhBF 4 , ((R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine)(COD)RhOTf, ((R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine)(NBD)RhBF 4 optionally comprising an additive selected from: BF 3 .IPA and BF 3 .MeOH.
7. The process according to claim 3 wherein:
R 1 is amido; R 2 is chlorine; R 3 is:
R a is
the hydrogen pressure is from 20 to 40 atmospheres,
the chiral catalyst is selected from:
(1) a chiral catalyst formed in situ by contacting a metal precursor, a ligand and optionally an activator; wherein the metal precursor is selected from:
(COD) 2 RhBF 4 , (COD) 2 RhOTf, (NBD) 2 RhBF 4 , (NBD) 2 RhOTf,
and (COD)Ru(methallyl) 2 ; the ligand is selected from: (R,S)-(di-t-butylphosphino)ferrocenyl-ethyldi-o-tolylphosphine, (R,S)-(diphenylphosphino)ferrocenyl-ethyldi-t-butylphosphine, (−)-TMBTP, (R)-hexaphemp, (R)-xyl-BINAP, the activator is absent or tetrafluoroboric acid; and
(2) a preformed catalyst complex: (−)-TMBTP(COD)RhBF 4 ;
additionally comprising an additive selected from: tetrafluoroboric acid, trifluoroacetic acid and BF 3 .MeOH.
8. The process according to claim 1 , wherein the enamide compound of formula (II):
wherein:
R 1 , R 2 , and R 3 are as defined in claim 1 ,
is prepared by treating a compound of formula (III):
with amide (IV):
in the presence of a base and a palladium catalyst;
wherein:
R 4 is selected from: aryl, heteroaryl and C 1-10 alkyl, wherein the aryl and heteroaryl moieties are unsubstituted or substituted with one to three R c substituents, and the alkyl moiety is unsubstituted or substituted with one or two R d substituents;
R 1 , R 2 , R 3 , R a , R b R c , R d , R e , and R f are as defined in claim 1 .
9. The process according to claim 8 , wherein:
R 1 is selected from amido and cyano;
R 2 is selected from hydrogen and chlorine;
R 3 is
R 4 is selected from phenyl, unsubstituted or substituted with an R c substituents;
and R a is:
10. The process according to claim 9 , wherein:
R 1 is cyano, R 2 is chlorine, R 3 is:
R 4 is 4-methylphenyl; and
R a is
the base is potassium carbonate, the palladium catalyst is selected from tris(dibenzylideneacetone) dipalladium(0), and bis(dibenzylideneacetone)palladium(0); and
the palladium catalyst additionally comprises a phosphine ligand selected from 1,4-bis(diphenylphosphino)butane, and 1,1′-bis(diisopropylphosphino)ferrocene.