Functionalized aluminum reagents

Description

BACKGROUND

Coordinative chain transfer polymerization (CCTP) using main group metals, i.e., a reversible chain transfer of polymeryl chains between chain growth active metal centers and chain growth inactive metal centers, has become an important strategy in insertion polymerization to reduce the amount of polymerization catalysts, to control the molecular weight and molecular weight distribution of polymers as well as to introduce chain end-functionalization by appropriate quenching of main group metal polymeryls. See Valente et al., Chem. Rev. 2013, 113, 3836-3857; Jian et al., Chem. Commun. 2010, 46, 3022-3024; German et al., Angew. Chem. Int. Ed. 2013, 52, 3438-3441. (b) Norsic et al., Angew. Chem. Int. Ed. 2015, 54, 4631-4635; Makio et al., J. Am. Chem. Soc. 2013, 135, 8177-8180.

Most commonly, commercially available un-functionalized aluminum and zinc alkyls have been employed, with zinc alkyls much better performing in terms of transfer efficiency and thus molecular weight control. With respect to heteroatom-functionalized main group metal alkyls, recently homoleptic di(ω-aminoalkyl) magnesium reagents have been used as chain transfer reagents to yield end functionalized amino polyethylenyl magnesiums (Ottou et al., Macromolecules 2017, 50, 8372-8377). Functionalized magnesium reagents were also employed to initiate polybutadiene chain growth to end-functionalized high trans polybutadiene (Leicht et al., Macromolecules 2018, 51, 763-770.), or with increased chain transfer numbers, to functionalized polybutadienes of less uniform stereochemistry (WO201013945).

In contrast, both in organic synthesis and in polymer chemistry, heteroatom-functionalized aluminum reagents have scarcely been used as synthetically useful reactants for the transfer of functional group substituted carbon nucleophiles probably owing to drawbacks in the synthesis of homoleptic aluminum alkyls or the expectedly low chemoselectivity of mixed aluminum alkyls (Xu et al., Acc. Chem. Res. 2016, 49, 2158-2168; Gao et al., J. Am. Chem. Soc., 2010, 132, 10961-10963; May et al., Org. Lett., 2011, 13, 3040-3043.)

SUMMARY

The present invention is directed to functionalized aluminum reagents of formula 1

where R is a linear or branched alkane group containing 1 to 8 carbon atoms, and R¹ is phenylene, or a linear or branched alkane diyl group containing 2 to 10 carbon atoms, or a combination of one or more phenylene groups and one or more linear or branched alkane diyl groups containing 1 to 10 carbon atoms; Q is of formula 2

where R³ and R⁴ are independently phenyl or a linear or branched alkyl group containing 1 to 10 carbon atoms, or R³ and R⁴ taken together with the nitrogen atom represent a nitrogen containing heterocyclic group containing from 4 to 12 carbon atoms.

The invention is further directed to a method of making functionalized aluminum reagents.

DESCRIPTION

There are disclosed functionalized aluminum reagents of formula 1

where R is a linear or branched alkane group containing 1 to 8 carbon atoms, and R¹ is phenylene, or a linear or branched alkane diyl group containing 2 to 10 carbon atoms, or a combination of one or more phenylene groups and one or more linear or branched alkane diyl groups containing 1 to 10 carbon atoms; Q is of formula 2

where R³ and R⁴ are independently phenyl or a linear or branched alkyl group containing 1 to 10 carbon atoms, or R³ and R⁴ taken together with the nitrogen atom represent a nitrogen containing heterocyclic group containing from 4 to 12 carbon atoms.

There is further disclosed a method of making functionalized aluminum reagents.

Functionalized aluminum reagents of formula 1 and 2 may be produced by reaction of a compound of formula 3 with a dialkyl aluminum hydride of formula 4

where R⁵ is phenylene, or a linear or branched alkane diyl group containing 1 to 9 carbon atoms, or a combination of one or more phenylene groups and one or more linear or branched alkane diyl groups containing 1 to 10 carbon atoms, and R is as previously defined.

The reaction of the compounds of formulas 3 and 4 may be done neat at a temperature ranging from 25 to 75 C for 12 to 36 hours. Optionally, the reaction may proceed in a hydrocarbon solvent in the presence of a neodymium (III) catalyst.

In one embodiment, the compound of formula 4 is diisobutyl aluminum hydride (DIBAL-H).

In various embodiment, the functionalized aluminum reagent of formula 1 may be one of the following compounds 1a-1l.

The functionalized aluminum reagents are useful, for example, as activators for lanthanide-based catalysts in polymerization of conjugated dienes.

The invention is further illustrated by the following non-limiting examples.

Example 1

(3-Diphenylaminopropyl)diisobutyl Aluminum (1a)

N,N-Diphenyl-N-allylamine (418 mg, 2 mmol), DIBAL-H (327 mg, 2.3 mmol), Nd(versatate)₃ (163 mg solution in hexanes, 100 μmol, 5 mol %), and 92 mg C₆D₆ were combined in an 8 mL screw-cap vial and stirred for 14 h at 323 K. The resulting solution contains 1 μmol Nd and ca 20 μmol of (3-Diphenylaminopropyl)diisobutyl aluminum (1a) per 10 mg solution and was used without further purification.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 7.06 (m, 4H, 2- and 6-H), 6.93 (m, 4H, 3- and 5-H), 6.83 (m, 2H, 4-H), 3.02 (t, ³J_HH=6.0 Hz, 2H, 7-H₂), 2.03 (n, ³J_HH=6.6 Hz, 2H, 2×(CH₃)₂CHCH₂Al), (1.76 (m, 2H, 8-H₂), 1.18 (d, ³J_HH=6.6 Hz, 12H, 2×(CH₃)₂CHCH₂Al), 0.53 (m, 2H, 9-H₂), 0.11 (d, ³J_HH=6.6 Hz, 4H, 2×(CH₃)₂CHCH₂Al). ¹³C NMR (100 MHz, C₆D₆, 300 K): δ 149.84 (C_q, C1), 129.04 (CH, C3 and C5), 126.56 (CH, C4), 124.80 (CH, C2 and C6), 60.51 (C7), 28.69 (2×(CH₃)₂CHCH₂Al), 27.13 (2×(CH₃)₂CHCH₂Al), 24.90 (2×(CH₃)₂CHCH₂Al), 22.04 (C8), 3.75 (C9).

Example 2

(5-Diphenylaminopentyl)diisobutyl Aluminum (1b)

N,N-Diphenyl-N-pent-4-enylamin (475 mg, 2 mmol), and DIBAL-H (291 mg, 2.05 mmol) were combined in a 8 mL screw-cap vial and stirred for 14 h at 323 K after which 1b had formed in ca 93% along with traces of isobutene.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 7.11 (m, 4H, 3- and 5-H), 7.01 (m, 4H, 2- and 6-H), 6.83 (m, 2H, 4-H), 3.54 (t, ³J_HH=7.3 Hz, 2H, 7-H₂), 1.95 (m, 2H, 2×(CH₃)₂CHCH₂Al), (1.63 (m, 2H, 8-H₂), 1.49 (m, 2H, 10-H₂), 1.31 (m, 2H, 9-H₂), 1.03 (d, ³J_HH=7.2 Hz, 12H, 2×(CH₃)₂CHCH₂Al), 0.3 (br, 6H, 11-H₂ and 2×(CH₃)₂CHCH₂Al). ¹³C NMR (100 MHz, C₆D₆, 300 K): δ 148.72 (C6), 129.51 (C3 and C5), 121.91 (C4), 121.42 (C2 and C6), 53.23 (C7), 33.13 (C9), 28.27 (2×(CH₃)₂CHCH₂Al), 27.21 (C8), 26.43 (2×(CH₃)₂CHCH₂Al), 25.56 (C10), 23.99 (br, 2×(CH₃)₂CHCH₂Al), 11.52 (br, C11).

Example 3

(3-(9H-carbazol-9-yl)propyl)diisobutyl Aluminum (1c)

N-Allylcarbazole (2073 mg, 10 mmol), and DIBAL-H (1500 mg, 10.5 mmol) were combined in a 8 mL screw-cap vial and stirred for 16 h at 323 K after which 1c had formed >95% along with traces of isobutene. 1c was alternatively prepared within 24 h at 298 K in the presence of 5 mol % Nd(versatate)₃.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 7.68 (m, 2H, 2-H), 7.19 (m, 2H, 4-H), 7.09 (m, 4H, 3- and 5-H), 3.40 (t, ³J_HH=6.6 Hz, 2H, 7-H₂), 1.80 (m, 2H, 8-H₂), 1.71 (m, 2H, 2×(CH₃)₂CHCH₂Al), 0.91 (d, ³J_HH=6.4 Hz, 12H, 2×(CH₃)₂CHCH₂Al), 0.06 (m, 2H, 9-H₂), −0.16 (m br, 4H, 2×(CH₃)₂CHCH₂Al). ¹³C NMR (100 MHz, C₆D₆, 300 K): δ 145.30 (C1), 126.68 (C4), 126.43 (C6), 122.17 and 112.85 (C3 and C5), 120.71 (C2), 53.88 (C7), 28.24 (2×(CH₃)₂CHCH₂Al), 26.24 (2×(CH₃)₂CHCH₂Al), 25.92 (C8), 24.40 (2×(CH₃)₂CHCH₂Al), 8.36 (C9).

Example 4

(5-(9H-carbazol-9-yl)pentyl)diisobutyl Aluminum (1d)

N-Pent-4-enylcarbazole (1177 mg, 5 mmol), and DIBAL-H (780 mg, 5.48 mmol) were combined in a 8 mL screw-cap vial and stirred for 16 h at 323 K after which 1d had formed >95% along with traces of isobutene. 1d was alternatively prepared within 4 h at 343K, or within 24 h at 298K in presence of 5 mol % Nd(versatate)₃.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 8.01 (m, 2H, 2-H), 7.37 (m, 2H, 4-H), 7.18 (m, 4H, 3- and 5-H), 3.81 (t, ³J_HH=6.8 Hz, 2H, 7-H₂), 1.90 (m, 2H, 2×(CH₃)₂CHCH₂Al), 1.56 (m, 2H, 8-H₂), 1.22 (m, 2H, 10-H₂), 1.14 (m, 2H, 9-H₂) 1.02 (d, ³J_HH=6.4 Hz, 12H, 2×(CH₃)₂CHCH₂Al), 0.21 (m, 4H, 4H, 2×(CH₃)₂CHCH₂Al), 0.35 (m br, 11-H₂). ¹³C NMR (100 MHz, C₆D₆, 300 K): δ 140.93 (C1), 125.90 (C4), 123.48 (C6), 120.79 (C2), 119.14 and 109.06 (C3 and C5), 42.92 (C7), 33.23 (C9), 28.73 (C8), 28.26 (2×(CH₃)₂CHCH₂Al), 26.30 (2×(CH₃)₂CHCH₂Al), 25.37 (C10), 24.8 (v br, 2×(CH₃)₂CHCH₂Al), 12.12 (C11).

Example 5

(3-(10H-phenothiazin-10-yl)propyl)diisobutyl Aluminum (1e)

N-Allylphenothiazin (1197 mg, 5 mmol), and DIBAL-H (700 mg, 4.92 mmol), and C₆D₆ (603 mg) were combined in a 8 mL screw-cap vial and stirred for 16 h at 323 K after which 1d had formed >90%. The resulting solution contains 20 μmol 1e per 10 mg solution.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 7.07, 6.87, and 6.69 (m:m:m, 2:2:4H, 2-H to 5-H), 3.45 (t, ³J_HH=5.2 Hz, 7-H₂), 2.00 (m, 2H, 8-H₂), 1.80 (m, 2H, 2×(CH₃)₂CHCH₂Al), 1.02 (br, 12H, 2×(CH₃)₂CHCH₂Al), 0.24 (t, ³J_HH=6.8 Hz, 9-H₂), −0.03 (br, 2×(CH₃)₂CHCH₂Al). ¹³C NMR (100 MHz, C₆D₆, 300 K): δ 146.02 and 122.78 (C1 and C6), 128.92, 128.24, 124.77, and 118.41 (C2-C5), 53.80 (C7), 28.49 (2×(CH₃)₂CHCH₂Al), 26.93 (2×(CH₃)₂CHCH₂Al), 25.18 (2×(CH₃)₂CHCH₂Al), 24.70 (C8), 8.93 (C9).

Example 6

(3-(1H-indol-1-yl)propyl)diisobutyl Aluminum (1f)

N-Allylindol (1572 mg, 10 mmol), and DIBAL-H (1480 mg, 10.4 mmol) were combined in a 8 mL screw-cap vial and stirred for 16 h at 323 K after which 1f had formed >95%.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 7.51, 7.14, and 7.05 (m each, 1:1:2H, 2-H to 5-H), 6.67 and 6.42 (br each, 1:1H, 7-H and 8-H), 3.43 (m br, 2H, 9-H₂), 1.79 (m br, 2H, 2×(CH₃)₂CHCH₂Al), 1.59 (m br, 10-H₂), 0.98 (d, ³J_HH=6.4 Hz, 12H, 2×(CH₃)₂CHCH₂Al), −0.09 (br, 6H, 11-H₂ and 2×(CH₃)₂CHCH₂Al). ¹³C NMR (100 MHz, C₆D₆, 300 K): δ 139.08 and 129.96 (C1 and C6), 126.48 and 105.28 (C7 and C8), 124.80, 122.45, 121.28, and 110.93 (C2-C5), 50.83 (C9), 28.30 (2×(CH₃)₂CHCH₂Al), 26.38 (2×(CH₃)₂CHCH₂Al), 26.13 (C10), 24.51 (2×(CH₃)₂CHCH₂Al), 9.82 (C11).

Example 7

(5-(1H-indol-1-yl)pentyl)diisobutyl Aluminum (1g)

N-Pent-4-enylindol (927 mg, 5 mmol), and DIBAL-H (720 mg, 5.06 mmol) were combined in a 8 mL screw-cap vial and stirred for 16 h at 323 K after which 1g had formed >95%.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 7.69 and 7.17 (m each, 1:3H, 2-H to 5-H), 6.90 and 6.45 (br each, 1:1H, 7-H and 8-H), 3.61 (m, 2H, 9-H₂), 1.92 (m, 2H, 2×(CH₃)₂CHCH₂Al), 1.54 (m, 2H, 10-H₂), 1.28 (m br, 2H, 12-H₂), 1.14 (m br, 2H, 11-H₂), 1.05 (d, ³J_HH=6.8 Hz, 12H, 2×(CH₃)₂CHCH₂Al), 0.20 (m br, 4H, 2×(CH₃)₂CHCH₂Al), −0.06 (m br, 2H, 13-H₂). ¹³C NMR (100 MHz, C₆D₆, 300 K): δ 137.10 and 129.66 (C1 and C6), 130.85 and 97.85 C7 and C8), 122.40, 121.74, 120.39, and 110.12 (C2-C5), 46.63 (C9), 33.02 (C11), 29.75 (C10), 28.37 (2×(CH₃)₂CHCH₂Al), 26.48 (2×(CH₃)₂CHCH₂Al), 25.54 (C12), 24.59 (2×(CH₃)₂CHCH₂Al), 11.65 (C13).

Example 8

(3-(3-methyl-1H-indol-1-yl)propyl)diisobutyl Aluminum (1h)

N-Allyl-3-methylylindol (856 mg, 5 mmol), and DIBAL-H (720 mg, 5.06 mmol) were combined in a 8 mL screw-cap vial and stirred for 16 h at 323 K after which 1g had formed >95%.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 7.33, 7.09, and 7.05 (m each, 1:1:2H, 2H to 5-H), 6.37 (s, 1H, 8-H), 3.31 (t, ³J_HH=6.2 Hz, 9-H₂), 2.06 (s, 3H, 12-H₃), 1.79 (m br, 2H, 10-H₂), 1.71 (m br, 2H, 2×(CH₃)₂CHCH₂Al), 0.91 (d, ³J_HH=6.8 Hz, 12H, 2×(CH₃)₂CHCH₂Al), 0.11 (m br, 2H, 11-H₂), −0.20 (m br, 4H, 2×(CH₃)₂CHCH₂Al). ¹³C NMR (100 MHz, C₆D₆, 300 K): δ 141.96 and 131.60 (C1 and C6), 124.6, 121.89, 120.43, and 112.47 (cC2-C5 and C8), 109.7 (C7), 52.44 (C9), 28.37 (2×(CH₃)₂CHCH₂Al), 26.40 (2×(CH₃)₂CHCH₂Al), 25.80 (C10), 23.73 (2×(CH₃)₂CHCH₂Al), 9.98 (C12), 8.77 (C11).

Example 9

(3-(indolin-1-yl)propyl)diisobutyl Aluminum (1i)

N-Allylindolin (796 mg, 4 mmol) and DIBAL-H (595 mg, 4.18 mmol) were combined in a 8 mL screw-cap vial and stirred for 16 h at 343 K after which 1i had formed >90%. Due to coordination of aluminum to the nitrogen atom, 7-11-CH₂ exhibit diastereotopic protons, likewise the iBu groups become fully diastereotopic.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 6.94 and 6.87 (m each, 1:2H, 3-, 4-, and 5-H), 6.78 (m, 1H, 2-H), 3.54 and 2.24 (m each, 1:1H, 8-H₂), 3.06 and 2.24 (m each, 1:1H, 9-H₂), 2.79 and 2.42 (m each, 1:1H, 7-H₂), 1.98 and 1.61 (m each, 1:1H, 10-H₂), 1.98 and 1.76 (2×(CH₃)₂CHCH₂Al), 1.10, 1.06, 0.99, and 0.86 (d each, ³J_HH=6.4 Hz, 12H, 2×(CH₃)₂CHCH₂Al), 0.29 (m, 2H, 11-H₂), −0.06 and −0.25 (m each, 2:2H, 2×(CH₃)₂CHCH₂Al). ¹³C NMR (100 MHz, C₆D₆, 300K): δ 149.11 (C1), 133.52 (C6), 127.26, 125.71, and 125.24 (C3-C5), 117.06 (C2), 63.03 (C9), 57.97 (C8), 28.87, 28.84, 28.78, 28.74, and 28.41 (2×(CH₃)₂CHCH₂Al and C7), 27.27 and 26.92 (2×(CH₃)₂CHCH₂Al), 23.51 (C10), 23.41 and 23.06 (2×(CH₃)₂CHCH₂Al), 4.58 (C11).

Example 11

(3-(phenyl(trimethylsilyl)amino)propyl)diisobutyl Aluminum (1k)

N-Allyl-N-phenyl-N-trimethylsilyamine (1097 mg, 5 mmol), DIBAL-H (782 mg, 5.5 mmol), Nd(versatate)₃ (407 mg solution in hexanes, 250 μmol), and 214 mg C₆D₆ were combined in a 8 mL screw-cap vial and stirred for 16 h at 343 K after which 1k had formed ca 95%. The solution contains 1 μmol Nd and ca 20 μmol 1k per 10 mg solution.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 6.95 and 6.85 (m each, 4:1H, 2-H to 5-H), 2.98 (t, ³J_HH=6.4 Hz, 7-H₂), 2.05 (m, 2H, 2×(CH₃)₂CHCH₂Al), 1.91 (m, 2H, 8-H₂), 1.16 (d, ³J_HH=6.4 Hz, 2×(CH₃)₂CHCH₂Al), 0.39 (m, 2H, 9-H₂), 0.22 (m br, 4H, 2×(CH₃)₂CHCH₂Al), −0.02 (s, 9H, TMS). ¹³C NMR (100 MHz, C₆D₆, 300K): δ 145.75 (C1), 128.37, 125.48, and 124.99 (C2-C5), 54.74 (C7), 28.75 (2×(CH₃)₂CHCH₂Al), 27.21 (2×(CH₃)₂CHCH₂Al), 26.00 (2×(CH₃)₂CHCH₂Al), 23.13 (C8), 3.28 (C9), 0.18 (TMS).

Example 12

(3-(pyrrolidin-1-yl)propyl)diisobutyl Aluminum (1l)

N-Allylpyrrolidin (556 mg, 5 mmol), DIBAL-H (740 mg, 5.2 mmol), Nd(versatate)₃ (163 mg solution in hexanes, 100 μmol, 2 mol %) were combined in a 8 mL screw-cap vial and stirred for 20 h at 343 K after which 1j had formed in ca 95%. Due to coordination of aluminum to the nitrogen atom, 1- and 2-CH₂ as well as (CH₃)₂CHCH₂Al exhibit diastereotopic protons.

¹H NMR (400 MHz, C₆D₆, 300 K): δ 2.85 and 1.84 (m each, 2:2H, 2×1-H₂), 2.17 (t, ³J_HH=6.0 Hz, 3-H₂), 1.95 (2×(CH₃)₂CHCH₂Al), 1.60 (m, 2H, 4-H₂), 1.48 and 1.34 (m each, 2:2H, 2×2-H₂), 1.08 (d, 3J_HH=7.6 Hz, 2×(CH₃)₂CHCH₂Al), 0.133 (t, ³J_HH=7.6 Hz, 5-H₂), −0.03 and −0.12 (dd each, ²J_HH=14.0 Hz, ³J_HH=7.6 Hz, 2×(CH₃)₂CHCH₂Al). ¹³C NMR (100 MHz, C₆D₆, 300K): δ 62.55 (C3), 54.98 (C1), 28.96 (2×(CH₃)₂CHCH₂Al), 27.35 (2×(CH₃)₂CHCH₂Al), 24.00 (C4), 23.00 (2×(CH₃)₂CHCH₂Al), 22.86 (C2), 4.66 (C5).