Synthesis and Enantioselective Diels−Alder Reactions of Optically Active Cobalt(III) Salen-1,3-butadien-2-yl Complexes

Chapman, John J.; Day, and Cynthia S.; Welker, Mark E.

doi:10.1021/om000074j

Cited by 12 publications

(7 citation statements)

References 17 publications

(11 reference statements)

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“…Thes tarting point of the investigation is the structure of (Salen)Co III ÀCH-(Me)OCOMe and the sequence of Equations (1), (2), and (3) in Scheme 3. Thes tarting complex is diamagnetic with as quare-pyramidal geometry,a se xperimentally found in several (Salen)Co III Xd erivatives,f or example,w ith X = Cl, Br,o rI , [29] O-3,5-C 6 H 3 F 2 , [30] COOMe, [19b] C(=CH 2 )CH= CH 2 , [31] and CONHR (R = CH(Me)Cy,C H 2 CCH, CH 2 -2-C 4 H 3 O). [32] Chelation by the acetate carbonyl group to yield a6 -coordinated isomer is endoergic,c ontrary to what was found for the bis(acetylacetonate) analogue,( acac) 2 Co III À CH(Me)OCOMe.…”

Section: Angewandte Chemiementioning

confidence: 99%

Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO₂‐Based Block Copolymers from Monomer Mixtures

et al. 2019

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Switchable polymerization provides the opportunity to regulate polymer sequence and structure in a one‐pot process from mixtures of monomers. Herein we report the use of O2 as an external stimulus to switch the polymerization mechanism from the radical polymerization of vinyl monomers mediated by (Salen)CoIII−R [Salen=N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamine; R=alkyl] to the ring‐opening copolymerization (ROCOP) of CO2/epoxides. Critical to this process is unprecedented monooxygen insertion into the Co−C bond, as rationalized by DFT calculations, leading to the formation of (Salen)CoIII−O−R as an active species to initiate ROCOP. Diblock poly(vinyl acetate)‐b‐polycarbonate could be obtained by ROCOP of CO2/epoxides with preactivation of (Salen)Co end‐capped poly(vinyl acetate). Furthermore, a poly(vinyl acetate)‐b‐poly(methyl acrylate)‐b‐polycarbonate triblock copolymer was successfully synthesized by a (Salen)cobalt‐mediated sequential polymerization with an O2‐triggered switch in a one‐pot process.

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Section: Angewandte Chemiementioning

confidence: 99%

Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO₂‐Based Block Copolymers from Monomer Mixtures

et al. 2019

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“…Scheme 2 The dienyl complex 4a from the (R,R)-salen ligand was characterized by X-ray crystallography. [3] The solid-state structure showed two distinct conformers (4a conformer 1 and 4a conformer 2) for this complex (Scheme 3) with equal solid-state conformer populations (ORTEPs of these conformers are also provided as Figure 1, a and b). These con- formers have dihedral (torsion) angles around the C(38)ϪC(39) and C(88)ϪC(89) bonds of 68Ϫ70°, similar to (dienyl)(glyoxime)cobalt complexes we have reported previously.…”

Section: Resultsmentioning

confidence: 86%

“…The two crystallographically independ- (7) 1.304(9) N(51)ϪC(57) 1.292(9) N(2)ϪC (14) 1.291(9) N(52)ϪC(64) 1.305(9) N(1)ϪC (8) 1.486 (7) N(51)ϪC(58) 1.484(7) N(2)ϪC (13) 1.494 (7) N(52)ϪC(63) 1.471(7) C(6)ϪC (7) 1. those we have observed previously for cobaltϪsp 2 -carbon bonds. [2,3,14] Crystal data and structure refinement parameters are provided in Table 3. Selected bond lengths for (2) 164.4(2) N(52)ϪCo (2)ϪO(51) 169.6(2) C(1)ϪO (1)ϪCo (1) 128.6(4) C(51)ϪO (51)ϪCo (2) 129.4(4) C(20)ϪO (2)ϪCo (1) 129.9(4) C(70)ϪO (52)ϪCo (2) 14)ϪN (2)ϪC (13) 119.4 (5) C(64)ϪN (52)ϪC (63) 122.5(5) C(14)ϪN (2)ϪCo (1) 126.1 (5) C(64)ϪN (52)ϪCo (2) 126.5(5) C(13)ϪN (2)ϪCo (1) 113.4(4) C(63)ϪN (52)ϪCo (2) 110.8(4) O(1)ϪC (1)ϪC (6) 122.9 (6) these complexes are provided in Table 4 and selected bond angles are provided in Table 5.…”

Section: Resultsmentioning

confidence: 99%

“…[2] Earlier, we communicated the synthesis of optically active (buta-1,3-dien-2-yl)(salen)Co complexes which underwent DielsϪAlder reactions with dimethyl fumarate with high enantioselectivity. [3] Many examples of chiral organic dienes have been reported, [4] but our report was the first use of optically active transition metal substituted dienyl complexes in enantioselective DielsϪAlder reactions. [5] Unactivated dienes such as buta-1,3-diene have proven to be difficult substrates for Lewis acid catalyzed enantioselective DielsϪAlder reactions, hence our search for buta-1,3-diene synthons.…”

Section: Introductionmentioning

confidence: 99%

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Enantioselective Diels−Alder Reactions of Optically Active (Buta-1,3-dien-2-yl)(salen)cobalt(III) Complexes

Chapman¹,

Day²,

Welker³

2001

Eur. J. Org. Chem.

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“…The cycloadduct trans-1,2-dicarbomethoxy-3-cyclohexene 42 is obtained in high optical activity yield by demetalation with sodium boron hydride, as shown in equation (51). 434 Yamada and coworkers have reported on many reactions with the bis(acetylacetone)ethylenediamine (BAE)-type fourcoordination cobalt complexes, e.g. enantioselective borohydride reductions, 443 -459 cyclopropanations, 460 -463 enantioselective hetero Diels-Alder reactions, 464 -467 enantioselective carbonyl-ene reactions, 468,469 enantioselective 1,3-dipolar cycloadditions, 470 -474 enantioselective Henry reactions, 475,476 and enantioselective CO 2 fixations, etc.…”

Section: Omaementioning

confidence: 99%

Three characteristic reactions of organocobalt compounds in organic synthesis

Omae

2007

Applied Organom Chemis

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Organocobalt compounds in organic synthesis have three characteristic reactions. The first occurs because cobalt has a high affinity to carbon-carbon π -bonds or carbon-nitrogen π -bonds. The second occurs because cobalt has a high affinity to carbonyl groups. The third is due to cobalt easily tending to form square-planar bipyramidal six-coordination structures with four nitrogen atoms or two nitrogen atoms and two oxygen atoms at the square-planar position, and to bond with one or two carbon atoms at the axial position. The first characteristic reactions are the representative reactions of organocobalt compounds with a mutually bridged bond between the two π -bonds of acetylene and the cobalt-cobalt bond of hexacarbonyldicobalt. These are reactions with a Co 2 (CO) 6 INTRODUCTIONOrganometallic intramolecular coordination compounds, especially five-membered ring compounds of organotin compounds, have been studied since 1965, and many reviews 1 -13 and some books 14 -16 have published on the subject. These compounds are mainly synthesized by cyclometalation reactions with transition metal compounds. The first publication on this subject is generally considered to be the reaction of diazobenzene with nick elocene by Kleiman and Dubeck 17 in 1963 as shown in equation (1).*Correspondence to: Iwao Omae, Nihon Pharmaceutical University, 10281, Komuro, Ina-cho, Saitama, An earlier article on the direct synthesis of 2-phenyl-3-indazolinone by carbonylation of azobenzene with a cobalt Materials, Nanoscience and CatalysisThree characteristic reactions of organocobalt compounds 319 carbonyl catalyst, as shown in equation (2), was published in 1956. 18 It was also synthesized in 1967 through a twostep reaction, that is, (i) cyclopalladation of azobenzene via the five-membered ring product, and (ii) carbonylation, as shown in equation (3). 19From these two reactions, the former reaction [equation (2)] is presumed also to proceed via cyclometallation, that is, cyclocobaltation with the cobalt carbonyl catalyst, as shown in equation (4). Actually, many cyclomatalations with cobalt compounds have been reported. 20 -35 For example, a similar cyclometalated organocobalt compound was prepared by the reaction of azobenzene with methyltetra(trimethylphosphine)cobalt, as shown in equation (5). 20 Further, one year previously, in 1955, the same type of heterocyclic compound was prepared by the same type of carbonylation reaction with an organocobalt compound, as shown in equation (6). 36 This publication by Murahashi 36 may be considered to be the first reaction relating cyclometalation reactions.In the chemical industry, organocobalt is an essential constituent in many important catalysts. Specifically, they are key components in the multimillion-pound technology of hydroformylation; that is, the catalytic transformation of olefins into aldehydes using homogeneous catalysts. This article reports on three characteristic reactions of the organocobalt compounds in organic syntheses on the basis of their structures and reactivities...

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Synthesis and Enantioselective Diels−Alder Reactions of Optically Active Cobalt(III) Salen-1,3-butadien-2-yl Complexes

Cited by 12 publications

References 17 publications

Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO₂‐Based Block Copolymers from Monomer Mixtures

Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO₂‐Based Block Copolymers from Monomer Mixtures

Enantioselective Diels−Alder Reactions of Optically Active (Buta-1,3-dien-2-yl)(salen)cobalt(III) Complexes

Three characteristic reactions of organocobalt compounds in organic synthesis

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Synthesis and Enantioselective Diels−Alder Reactions of Optically Active Cobalt(III) Salen-1,3-butadien-2-yl Complexes

Cited by 12 publications

References 17 publications

Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO2‐Based Block Copolymers from Monomer Mixtures

Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO2‐Based Block Copolymers from Monomer Mixtures

Enantioselective Diels−Alder Reactions of Optically Active (Buta-1,3-dien-2-yl)(salen)cobalt(III) Complexes

Three characteristic reactions of organocobalt compounds in organic synthesis

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Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO₂‐Based Block Copolymers from Monomer Mixtures

Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO₂‐Based Block Copolymers from Monomer Mixtures