Syntheses and thermal reactivities of symmetrically and asymmetrically substituted acyclic enediynes: steric control of Bergman cyclization temperatures

Rawat, Diwan S.; Zaleski, Jeffrey M.

doi:10.1039/b007360l

Cited by 41 publications

(47 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Large, irreversible exothermic peaks are observed between 100-210°C upon heating of all enediyne macrocycles (86)(87)(88)(89)(90)(91)(92). Overall, the cyclization temperatures of these macrocyclic ligands (86,87,90) are more than 50°C lower than the benzannulated tetraazaenediyne ligand prepared from an alternative synthetic approach by Basak.…”

Section: Macrocyclic Complexes Of Copper and Zincmentioning

confidence: 89%

“…From this reaction, the chloroenyne synthon 73 is produced as a very useful side product for the synthesis of asymmetric enediynes. 88 results, in the solid state, the tetrahedral Cu(I) complex cycloaromatizes at 203°C, while its geometrically more constrained tetragonal Cu(II) counterpart cycloaromatizes at 121°C. Comparable results are also obtained for the monoenediyne analogues of the same oxidation states.…”

Section: (E/z)-55mentioning

confidence: 91%

“…Although the temperature decrease is modest, it is consistent with trends observed in other metal binding enediyne ligands as a function of ligand rigidity. 88,119,122 The Cu(II) complex of tact1:1, 88, exhibits a Bergman cyclization temperature of 121°C. The cyclization temperature is nearly identical to those reported for other [Cu(N) 4 ] 2+ metalloenediyne constructs whose tetragonal X···Cu(N 4 )···X structures have been characterized by EPR, ligand field region electronic absorption spectroscopy, and molecular mechanics calculations.…”

Section: Macrocyclic Complexes Of Copper and Zincmentioning

confidence: 99%

See 2 more Smart Citations

Geometric and Electronic Control of Thermal Bergman Cyclization

Rawat¹,

Zaleski²

2004

Synlett

Self Cite

View full text Add to dashboard Cite

The geometric and electronic contributions to Bergman cyclization of simple enediynes are compared and contrasted to those of recently developed metalloenediyne analogues. The comparison reveals that metals can have more diverse, subtle, and in some cases, more dramatic geometric effects upon Bergman cyclization than simple substitution chemistry. In addition to geometric consequences imposed by metals, electronic control of metalloenediyne cyclization is emerging as a complementary parameter in complex design.

show abstract

Section: Macrocyclic Complexes Of Copper and Zincmentioning

confidence: 89%

Section: (E/z)-55mentioning

confidence: 91%

Section: Macrocyclic Complexes Of Copper and Zincmentioning

confidence: 99%

See 1 more Smart Citation

Geometric and Electronic Control of Thermal Bergman Cyclization

Rawat¹,

Zaleski²

2004

Synlett

Self Cite

View full text Add to dashboard Cite

show abstract

“…The effect of p-conjugation is weak. Rawat and Zaleski [40] demonstrated steric effect of functional groups in terminal acyclic enediynes on their cycloaromatization according to Bergman. Rawat and Zaleski [40] demonstrated steric effect of functional groups in terminal acyclic enediynes on their cycloaromatization according to Bergman.…”

Section: Ii3 Effect Of Electronic Factors On the Formation Of Diradmentioning

confidence: 99%

10.1007/s11176-008-2012-z

2010

CrossRef Listing of Deleted DOIs

View full text Add to dashboard Cite

The review summarizes synthetic approaches to enediynes and enyne3allenes that are responsible for a Bergman and Myers3Saito cycloaromatizations resulting in the formation of benzene, b-substituted naphthalene, and acene derivatives. Cycloaromatization paths leading to fulvene and indene systems in the presence of radical and ionic initiators, as well as of metal catalysts, are discussed. Practical importance of the syntheses is noted.

show abstract

“…In a recent paper Alabugin [13] evaluated the stereoelectronic effects in cyclohexane-, 1,3-dioxane-, 1,3-oxathiane-, and 1,3-dithiane- [ based enediynes. Zaleski et al [14] have shown how dramatically the steric influences of the functional groups at the termini of acyclic enediynes can affect the Bergman cyclization (BC) temperatures of the resulting compounds. In this communication, we wish to describe, for the first time, the synthesis and characterization of a series of donor-acceptor (D/A) containing 1,2-dialkynylbenzenes (Figure 1) and the effect of CT complexation and π-π interactions on the kinetics of the BC.…”

mentioning

confidence: 99%

The Effect of Charge‐Transfer Complexation/π‐Stacking Interactions in Lowering the Activation Barrier of the Bergman Cyclization

2005

View full text Add to dashboard Cite

To elaborate the concept of weak interactions and their effect on Bergman Cyclization (BC), several 1,2-dikynyl benzenes incorporating various combinations of donor and acceptor units in the two arms of the enediynes were designed and synthesized, and their charge-transfer interactions followed by UV/Vis spectroscopy. The thermal reactivities, as studied by DSC, show an increase in reactivity for the donor/acceptor More than fifty years ago, Mulliken [1] suggested that charge-transfer (CT) complexes "may afford new possibilities for understanding intermolecular interactions in biological systems". This statement proved to be true after several biochemical phenomena were explained on the basis of CT complex formation. [2][3][4][5] CT complexes arising from the interaction of aromatic π-donor and -acceptor molecules have been studied extensively. However, fewer intramolecular CT analogs have been reported, primarily of the cyclophane type, in which the donor and acceptor portions are locked together in a rather rigid arrangement.[6] More flexible intramolecular CT complexes have been reported in a recent communication, whereby a cyclohexane skeleton is substituted at adjacent trans positions with aromatic donor and acceptor groups.[7] Besides charge-transfer interactions, attractive, nonbonding interactions between aromatic units (π-stacking) play a central role in many areas of chemistry and biochemistry, the most notable ones being in molecular recognition and self-assembly, [8] in base-pair stacking in DNA, [9] and in controlling the tertiary structure of proteins, [10] and hence are of interest to all realms of chemistry and biology. The activity profiles of the well-known, medicinally important enediynes are greatly perturbed by weak interactions.[11] Jones et al. [12] have shown that strong electron-withdrawing groups increase the barrier for Bergman cyclization, while σ-donating groups decrease it; π-conjugation, in particular donation, has little effect. In a recent paper Alabugin [13] evaluated the stereoelectronic effects in cyclohexane-, 1,3-dioxane-, 1,3-oxathiane-, and 1,3-dithiane- [ based enediynes. Zaleski et al. [14] have shown how dramatically the steric influences of the functional groups at the termini of acyclic enediynes can affect the Bergman cyclization (BC) temperatures of the resulting compounds. In this communication, we wish to describe, for the first time, the synthesis and characterization of a series of donor-acceptor (D/A) containing 1,2-dialkynylbenzenes (Figure 1) and the effect of CT complexation and π-π interactions on the kinetics of the BC. The corresponding D/D and A/A counterparts were also synthesized to compare the reactivities towards BC. Incidentally, aromatic 1,2-dialkynyl systems have been considered in the literature [15] to be a variant of Figure 1. Representation of donor-acceptor-containing enediynyl compounds.

show abstract

Syntheses and thermal reactivities of symmetrically and asymmetrically substituted acyclic enediynes: steric control of Bergman cyclization temperatures

Cited by 41 publications

References 16 publications

Geometric and Electronic Control of Thermal Bergman Cyclization

Geometric and Electronic Control of Thermal Bergman Cyclization

10.1007/s11176-008-2012-z

The Effect of Charge‐Transfer Complexation/π‐Stacking Interactions in Lowering the Activation Barrier of the Bergman Cyclization

Contact Info

Product

Resources

About