Metathesis catalysts and methods thereof
The present application provides, among other things, compounds and methods for metathesis reactions. In some embodiments, a provided compound has the structure of formula I, II or III. In some embodiments, R 1 of formula I, II or III comprises an electron-withdrawing group. In some embodiments, the present invention provides methods for preparing provided compounds.
1. A compound of formula I, or II:
wherein:
M is molybdenum or tungsten;
R 1 is substituted phenyl, wherein one to five of the substituents are independently R y ;
each of R 2 and R 3 is independently R, —OR, —SR, —N(R) 2 , —OC(O)R, —SOR, —SO 2 R, —SO 2 N(R) 2 , —C(O)N(R) 2 , —NRC(O)R, or —NRSO 2 R;
R 2′ and R 3′ are taken together with M to form a substituted 3-8 membered saturated or partially unsaturated ring having, in addition to M, 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each of R 4 and R 5 is independently triflate, —O-2,6-(CHPh 2 ) 2 -4-MeC 6 H 2 , DFTO, —OC(CF 3 ) 3 or —OC(C 6 F 5 ) 3 ;
R y is independently an electron-withdrawing group;
each R is independently hydrogen or an optionally substituted group selected from C 1-20 aliphatic, C 1-20 heteroaliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; or:
two R groups are optionally taken together with the intervening atoms to form an optionally substituted 3-10 membered, monocyclic or bicyclic, saturated, partially unsaturated, or aryl ring having, in addition to the intervening atoms, 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
n is 0-2; and
each R 6 is independently a neutral ligand.
2. The compound of claim 1 , wherein the compound is a compound of formula I, and one of R 2 and R 3 is hydrogen and the other is optionally substituted C 1-20 aliphatic.
3. The compound of claim 1 , wherein the compound is a compound of formula II, and R 2′ and R 3′ are taken together with M to form a 3-membered saturated ring unsubstituted at the ring carbon atoms.
4. The compound of claim 1 , wherein each of R 4 and R 5 is DFTO, or —OC(C 6 F 5 ) 3 .
5. The compound of claim 1 , wherein M is tungsten.
6. A compound of formula I, or II:
wherein:
M is tungsten;
R 1 is
each of R 2 and R 3 is independently R, —OR, —SR, —N(R) 2 , —OC(O)R, —SOR, —SO 2 R, —SO 2 N(R) 2 , —C(O)N(R) 2 , —NRC(O)R, or —NRSO 2 R;
R 2′ and R 3′ are taken together with M to form a substituted 3-8 membered saturated or partially unsaturated ring having, in addition to M, 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each of R 4 and R 5 is independently —OR, —OSi(R) 3 , or —OAr a ;
Ar a is
m is 0-3;
Ring B is a substituted group selected from phenyl or a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
p is 1-5;
q is 0-5;
t is 0-4;
each of Ring B′, Ring C and Ring D is independently a substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-14 membered bicyclic or tricyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each R 7 is independently halogen, R, —CN, —NO 2 , —OR, —SR, —S(O)R, —S(O) 2 R, —OSi(R) 3 , —N(R) 2 , —NRC(O)R, —NRC(O)OR, —NRC(O)N(R) 2 , —NRSO 2 R, —NRSO 2 N(R) 2 , or —NROR;
each of R x , R y and R z is independently an electron-withdrawing group;
each R is independently hydrogen or an optionally substituted group selected from C 1-20 aliphatic, C 1-20 heteroaliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; or:
two R groups are optionally taken together with the intervening atoms to form an optionally substituted 3-10 membered, monocyclic or bicyclic, saturated, partially unsaturated, or aryl ring having, in addition to the intervening atoms, 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
n is 0-2; and
each R 6 is independently a neutral ligand.
7. The compound of claim 6 , wherein R 1 is
8. The compound of claim 6 , wherein each of R 4 and R 5 is independent —OAr a , wherein Ar a is
9. The compound of claim 1 , wherein n is 1.
10. A compound of formula I, or II, or III:
wherein:
M is molybdenum or tungsten;
R 1 is substituted phenyl, wherein one to five of the substituents are independently R y ;
each of R 2 and R 3 is independently R, —OR, —SR, —N(R) 2 , —OC(O)R, —SOR, —SO 2 R, —SO 2 N(R) 2 , —C(O)N(R) 2 , —NRC(O)R, or —NRSO 2 R;
R 2′ and R 3′ are taken together with M to form a substituted 3-8 membered saturated or partially unsaturated ring having, in addition to M, 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each of R 4 and R 5 is independently halogen, R, —N(R) 2 , —NRC(O)R, —NRC(O)OR, —NRC(O)N(R) 2 , —NRSO 2 R, —NRSO 2 N(R) 2 , —NROR, —OR, —OSi(R) 3 , —OAr a , or an optionally substituted group selected from a 5-6 membered monocyclic heteroaryl ring having at least one nitrogen and 0-3 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having at least one nitrogen and 0-2 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having at least one nitrogen and 0-4 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having at least one nitrogen and 0-4 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur;
Ar a is
m is 0-3;
Ring B is a substituted group selected from phenyl or a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
p is 1-5;
q is 0-5;
t is 0-4;
each of Ring B′, Ring C and Ring D is independently a substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-14 membered bicyclic or tricyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each R 7 is independently halogen, R, —CN, —NO 2 , —OR, —SR, —S(O)R, —S(O) 2 R, —OSi(R) 3 , —N(R) 2 , —NRC(O)R, —NRC(O)OR, —NRC(O)N(R) 2 , —NRSO 2 R, —NRSO 2 N(R) 2 , or —NROR,
each of R x , R y and R z is independently an electron-withdrawing group;
each R is independently hydrogen or an optionally substituted group selected from C 1-20 aliphatic, C 1-20 heteroaliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; or:
two R groups are optionally taken together with the intervening atoms to form an optionally substituted 3-10 membered, monocyclic or bicyclic, saturated, partially unsaturated, or aryl ring having, in addition to the intervening atoms, 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
n is 1; and
R 6 is a bidentate ligand, and R 6 is 1,2-dimethoxyethane (DME).
11. The compound of claim 1 , wherein n is 0.
12. A compound selected from: W(NAr cl3 )(CHCMe 3 )(OTf) 2 (DME), W(NAr cl3 )(CHCMe 3 )(2,5-Me 2 Pyr) 2 , W(NAr Br3 )(CHCMe 3 )(OTf) 2 (DME), W(NAr Cl2CF3 ) 2 (CHCMe 3 )(OTf) 2 (DME), W(NAr (CF3)2 )(CHCMe 3 )(OTf) 2 (DME), Mo(NC 6 F 5 )(CHCMe 2 Ph)(OTf) 2 (DME), Mo(NC 6 F 5 )(CHCMe 2 Ph)(Me 2 Pyr) 2 , Mo(NC 6 F 5 )(CHCMe 2 Ph)[OC(CF 3 ) 3 ] 2 , Mo(NC 6 F 5 )(CHCMe 2 Ph)[OC(C 6 F 5 ) 3 ] 2 , Mo(NC 6 F 5 )(CHCMe 2 Ph)(ODFT) 2 , W(NC 6 F 5 )(CH-t-Bu)(DME)(OTf) 2 , W(NC 6 F 5 )(CH-t-Bu)(THF) 2 (OTf) 2 , W(NC 6 F 5 )(CH-t-Bu)(DME)(THF)(OTf) 2 , [W(NC 6 F 5 )(CH-t-Bu)(t-DME)(OTf) 2 ] x , W(NC 6 F 5 )(CH-t-Bu)(DME)(Pyr) 2 , W(NC 6 F 5 )(CH-t-Bu)(DME)[OC(CF 3 ) 3 ] 2 , W(NC 6 F 5 )(CH-t-Bu)[OC(C 6 F 5 ) 3 ] 2 , W(NC 6 F 5 )(CH-t-Bu)(ODFT) 2 , Mo(NC 6 F 5 )(CHCMe 2 Ph)(Me 2 Pyr)(HMTO), W(NC 6 F 5 )(CH-t-Bu)(dme) 1.5 (Pyr) 2 , W(NC 6 F 5 )(CHCMe 2 Ph)(Me 2 Pyr)(HMTO), W(NAr cl3 )(CH-t-Bu)(Pyr)(DFTO), W(NAr cl3 )(CH-t-Bu)(Pyr)(HMTO), W(NAr cl3 )(CH-t-Bu)(Pyr)(HIPTO), W(NAr Br3 )(CH-t-Bu)(Pyr)(DFTO), W(NAr Br3 )(CH-t-Bu)(Pyr)(HMTO), W(NAr Br3 )(CH-t-Bu)(Pyr)(HIPTO), W(NAr Cl2CF3 )(CH-t-Bu)(Pyr)(DFTO), W(NAr Cl2CF3 )(CH-t-Bu)(Pyr)(HMTO), W(NAr Cl2CF3 )(CH-t-Bu)(Pyr)(HIPTO), W(NAr (CF3)2 )(CH-t-Bu)(Pyr)(DFTO), W(NAr (CF3)2 )(CH-t-Bu)(Pyr)(HMTO), W(NAr (CF3)2 )(CH-t-Bu)(Pyr)(HIPTO), W(NAr cl3 )(CH-t-Bu)(OR F6 ), W(NAr cl3 )(CH-t-Bu)(OR F9 ), W(NAr Br3 )(CH-t-Bu)(OR F6 ), W(NAr Br3 )(CH-t-Bu)(OR F9 ), W(NAr Cl2CF3 )(CH-t-Bu)(OR F6 ), W(NAr Cl2CF3 )(CH-t-Bu)(OR F9 ), W(NAr (CF3)2 )(CH-t-Bu)(OR F6 ), W(NAr (CF3)2 )(CH-t-Bu)(OR F9 ), W(NAr Cl3 )(CHCMe 3 )(Me 2 Pyr)(OHMT), W(NAr cl3 )(CHCMe 3 )(Me 2 pyr)(ODFT), W(NAr cl3 )(CHCMe3)(Me 2 pyr)(OTript), W(NAr cl3 )(CHCMe 3 )(ODBMP) 2 , W(NAr Br3 )(CHCMe 3 )(ODBMP) 2 , W(NAr Cl2CF3 )(CHCMe 3 )(ODBMP) 2 , W(NAr (CF3)2 )(CHCMe 3 )(ODBMP) 2 , W(NAr (CF3)2 )(CHCMe 3 )(ODBMP) 2 ·2DME, W(NAr cl )(CHCMe 3 )(OTf) 2 (dme), W(NAr cl )(CHCMe 3 )(ODBMP) 2 , W(NAr F )(CHCMe 3 )(OTf) 2 (dme), W(NAr F )(CHCMe 3 )(ODBMP) 2 , W(NAr′)(CHCMe 3 )(OTf) 2 (dme), W(NAr′)(CHCMe 3 )(ODBMP) 2 , W(NAr″)(CHCMe 2 Ph)(OTf) 2 (dme), W(NAr″)(CHCMe 2 Ph)(ODBMP) 2 , W(NC 6 F 5 )(CH 2 CH 2 CH 2 )[OC(CF 3 ) 3 ] 2 , Mo(NC 6 F 5 ) 2 Cl 2 (DME), W(NC 6 F 5 ) 2 Cl 2 (DME), Mo(NC 6 F 5 ) 2 (CH 2 CMe 2 Ph) 2 , Mo(NC 6 F 5 ) 2 (CH 2 CMe 2 Ph) 2 (Et 2 O), W(NC 6 F 5 ) 2 (CH 2 CMe 3 ) 2 , W(NAr cl3 ) 2 Cl 2 (DME), W(NAr cl3 ) 2 (CH 2 CMe 3 ) 2 , W(NAr Br3 ) 2 Cl 2 (DME), W(NAr Br3 ) 2 (CH 2 CMe 3 ) 2 , W(NAr Cl2CF3 ) 2 Cl 2 (DME), W(NAr Cl2CF3 ) 2 (CH 2 CMe 3 ) 2 , W(NAr (CF3)2 ) 2 Cl 2 (DME), and W(NAr (CF3)2 ) 2 (CHCMe 3 ) 2 , wherein Ar cl3 is 2,4,6-trichlorophenyl, Ar Br3 is 2,4,6-tribromophenyl, Ar Cl2CF3 is 2,6-dichloro-4-(trifluoromethyl)phenyl, Ar (CF3)2 is 3,5-bis(trifluoromethyl)phenyl, OR F6 is hexafluoro-tert-butoxide (—OCMe(CF 3 ) 2 ), OR F9 is perfluoro-tert-butoxide (—OC(CF 3 ) 3 ), Ar′ is 2,6-Me 2 C 6 H 3 , and Ar″ is 3,5-Me 2 C 6 H 3 , or HO-2,6-(CHPh 2 ) 2 -4-MeC 6 H 2 or a salt thereof.
13. The compound of claim 12 , wherein the compound is HO-2,6-(CHPh 2 ) 2 -4-MeC 6 H 2 or a salt thereof.
14. A compound of formula I, or II, or III:
wherein:
M is tungsten;
R 1 is
each of R 2 and R 3 is independently R, —OR, —SR, —N(R) z , —OC(O)R, —SOR, —SO 2 R, SO 2 N(R) 2 , —C(O)N(R) 2 , —NRC(O)R or —NRSO 2 R;
R 2′ and R 3′ are taken together with M to form a substituted 3-8 membered saturated or partially unsaturated ring having, in addition to M, 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each of R 4 and R 5 is independently halogen, R, —N(R) 2 , —NRC(O)R, —NRC(O)OR, —NRC(O)N(R) 2 , —NRSO 2 R, —NRSO 2 N(R) 2 , —NROR, —OR, —OSi(R) 3 , —OAr a , or an optionally substituted group selected from a 5-6 membered monocyclic heteroaryl ring having at least one nitrogen and 0-3 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having at least one nitrogen and 0-2 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having at least one nitrogen and 0-4 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having at least one nitrogen and 0-4 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur;
Ar a is
m is 0-3;
Ring B is a substituted group selected from phenyl or a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
p is 1-5;
q is 0-5;
t is 0-4;
each of Ring B′, Ring C and Ring D is independently a substituted group selected from phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-14 membered bicyclic or tricyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
each R 7 is independently halogen, R, —CN, —NO 2 , —OR, —SR, —S(O)R, —S(O) 2 R, —OSi(R) 3 , —N(R) 2 , —NRC(O)R, —NRC(O)OR, —NRC(O)N(R) 2 , —NRSO 2 R, —NRSO 2 N(R) 2 , or —NROR;
each of R x , R y and R z is independently an electron-withdrawing group;
each R is independently hydrogen or an optionally substituted group selected from C 1-20 aliphatic, C 1-20 heteroaliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; or:
two R groups are optionally taken together with the intervening atoms to form an optionally substituted 3-10 membered, monocyclic or bicyclic, saturated, partially unsaturated, or aryl ring having, in addition to the intervening atoms, 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
n is 0-2; and
each R 6 is independently a neutral ligand.
15. The compound of claim 14 , wherein the compound is a compound of formula II.
16. The compound of claim 14 , wherein the compound is a compound of formula III.
17. The compound of claim 14 , wherein the compound is a compound of formula II, and R 2′ and R 3′ are taken together with M to form a metallacyclobutane ring optionally substituted at the ring carbon atoms.
18. The compound of claim 17 , wherein R 2′ and R 3′ are taken together with M to form a metallacyclobutane ring unsubstituted at the ring carbon atoms.
19. The compound of claim 14 , wherein the compound is a compound of formula II, and R 2′ and R 3′ are taken together with M to form a metallacyclopropane ring optionally substituted at the ring carbon atoms.
20. The compound of claim 14 , wherein the compound is a compound of formula I.
21. The compound of claim 20 , wherein each of R 4 and R 5 is independently —N(R) 2 , or an optionally substituted group selected from a 5-6 membered monocyclic heteroaryl ring having at least one nitrogen and 0-3 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having at least one nitrogen and 0-2 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having at least one nitrogen and 0-4 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, and an 8-10 membered bicyclic heteroaryl ring having at least one nitrogen and 0-4 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur; wherein each of R 4 and R 5 is bonded to M through the nitrogen atom.
22. The compound of claim 21 , wherein each of R 4 and R 5 is independent optionally substituted pyrrolyl.
23. The compound of claim 14 , wherein the compound is a compound of formula I or II, wherein:
R 4 is —N(R) 2 , or an optionally substituted group selected from a 5-6 membered monocyclic heteroaryl ring having at least one nitrogen and 0-3 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3-7 membered saturated or partially unsaturated heterocyclic ring having at least one nitrogen and 0-2 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having at least one nitrogen and 0-4 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur, and an 8-10 membered bicyclic heteroaryl ring having at least one nitrogen and 0-4 additional heteroatoms independently selected from nitrogen, oxygen, or sulfur; wherein R 4 is bonded to M through the nitrogen atom; and
R 5 is —OR, —OSi(R) 3 , or —OAr a .
24. The compound of claim 23 , wherein R 4 is optionally substituted pyrrolyl.
25. The compound of claim 23 , wherein R 5 is —OAr a , wherein Ar a is
26. The compound of claim 14 , wherein the compound is a compound of formula I or II, and each of R 4 and R 5 is independently —OR, —OSi(R) 3 , or —OAr a .
27. The compound of claim 26 , wherein each of R 4 and R 5 is independently —OAr a , wherein Ar a is
28. The compound of claim 14 , wherein the compound is a compound of formula III, wherein each of R 4 and R 5 is independently optionally substituted C 1-20 aliphatic.
29. The compound of claim 10 , wherein:
R 1 is substituted phenyl, wherein three to five of the substituents are independently R y ; and each of R x , R y and R z is independently halogen or —CF 3 .