Synthesis of a 9,11-bis-desoxy-prostaglandin

Crabbé, Pierre; Cervantes, A.; Guzmán, A.

doi:10.1016/s0040-4039(01)84525-1

Cited by 8 publications

(3 citation statements)

References 5 publications

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“…The intramolecular Michael addition product 23 , isolated in a 25% yield (0.28 mmol) when an RVC cathode was used, displayed the following characteristics: TLC R f 0.25 (SiO 2 , 30% Et 2 O/petroleum ether), vanillin; IR (neat) 2952, 2870, 2718, 1720, 1436, 1247, 1194, 1175, 1010, 916, 851, 731 cm -1 ; 1 H NMR (CDCl 3 , 400 MHz) δ 9.61 (d, J = 3.1 Hz, 1H), 3.65 (s, 3H), 2.58 (m, 1H), 2.45 (m, 2H), 1.98 (m, 1 H), 1.9 (m, 2H), 1.7 (m, 2H), 1.3−1.2 (m, 2H); 13 C NMR (CDCl 3 , 100 MHz) δ 203.4, 173.1, 57.6, 51.8, 39.1, 37.3, 33.0, 26.9, 24.9. The 1 H NMR and IR data matched those reported previously …”

Section: Methodssupporting

confidence: 85%

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Indirect Electroreductive Cyclization and Electrohydrocyclization Using Catalytic Reduced Nickel(II) Salen

Miranda

Wade²,

Little³

2005

J. Org. Chem.

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[Chemical reaction: See text] We describe efforts to achieve the electroreductive cyclization (ERC) and the electrohydrocyclization (EHC) reactions using catalytic nickel(II) salen as a mediator. While nickel(II) salen proved effective, the analogous cobalt complex as well as nickel(II) cyclam were not. The transformations were achieved in yields ranging from 60 to 94% using either a mercury pool or an environmentally preferable reticulated vitreous carbon (RVC) cathode. These examples represent the first instances wherein a nickel salen complex has been used in this manner. Clear differences between the voltammetric behavior of the ERC and EHC substrates were observed. The bisenoate 14, for example, displays a substantially larger catalytic current. When the structurally modified mediator 31 was used, the electron-transfer pathway shuts down. Instead, the reduced form of 31 behaves as an electrogenerated base, leading to the formation of the intramolecular Michael adduct 23. Presumably, the methyl groups of the modified ligand diminish the ability of the reduced form of the complex to serve as a nucleophile but not as a base. Aldehyde 23 was also characterized as a side product of the nickel(II) salen mediated electroreductive cyclization of 11. Given that it is absent from nonmediated processes, its formation is linked to the presence of the mediator. To account for the results, we favor the existence of a mechanistic continuum involving an equilibrium between nickel(II) salen (15) and two reduced forms, one being the metal-centered species 16, the other being a ligand-centered species 17. We postulate that one form may be more prominently involved with the chemistry than another, depending upon the electronic properties/requirements of the substrate, and suggest that the equilibrium will shift to accommodate the need. Thus, for a hard electrophile like an alkyl halide, the properties of 16 ought to dominate, whereas 17 ought to predominate as the reactive species accounting for the chemistry described herein since it properly matches a soft ligand-centered nucleophile with a soft electron deficient alkene.

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Section: Methodssupporting

confidence: 85%

“…The 1 H NMR and IR data matched those reported previously. 35 (2-Hydroxy-2-methyl-cyclohexyl)-acetic Acid Methyl Ester (19). Methyl ketone 12 (268 mg, 1.45 mmol) was transformed into the cyclized hydroxy ester 19 by following the general procedure described above.…”

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confidence: 99%

Indirect Electroreductive Cyclization and Electrohydrocyclization Using Catalytic Reduced Nickel(II) Salen

Miranda

Wade²,

Little³

2005

J. Org. Chem.

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“…Compound 24 has been previously used in prostaglandin syntheses. 36,37 The aldehyde-enoate ester substrate (25) that might have formed a seven-membered ring did not cyclize under our reaction conditions. Enoate ester 26, too, was unreactive, which is consistent with Baldwin's ring closure rules.…”

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confidence: 91%

Catalytic Intramolecular Conjugate Additions of Aldehyde-Derived Enamines to α,β-Unsaturated Esters

et al. 2020

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We report a pairing of known catalysts that enables intramolecular conjugate additions of aldehyde-derived enamines to α,β-unsaturated esters. Despite extensive prior exploration of conjugate additions of aldehyde-derived enamines, catalytic conjugate additions to unactivated enoate esters are unprecedented. Achieving enantioselective and diastereoselective six-membered ring formation requires the coordinated action of a chiral pyrrolidine, for nucleophilic activation of the aldehyde via enamine formation, and a hydrogen bond donor, for electrophilic activation of the enoate ester. Proper selection of the hydrogen bond donor is essential for chemoselectivity, which requires minimizing competition from homoaldol reaction. Utility is demonstrated in a six-step synthesis of (−)-yohimbane from cycloheptene.Letter pubs.acs.org/OrgLett

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