Synthese und Solvolyse cyclischer Dieninyl‐triflate

Hanack, Michael; Rieth, Robert

doi:10.1002/cber.19871201009

Cited by 17 publications

(7 citation statements)

References 13 publications

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“…Yields of the substitution products were greatly improved by use of the cyclic dienyne 54 (Scheme ) . The strained-ring system raises the ground state energy of 54 as compared to 49 and favors the cyclization pathway over elimination.…”

Section: Nucleophilic Attack By the Alkynementioning

confidence: 99%

Acceleration of Conjugated Dienyne Cycloaromatization

Hitt

O’Connor

2011

Chem. Rev.

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The most surprising observation was the high degree of rate acceleration in the presence of amine bases, which was determined to be an order of magnitude higher than molecular oxygen acceleration and 4 orders of magnitude higher than hydrogen abstraction from solvent. Use of C-2 deuterium enriched 9 with amine showed high levels of D incorporation in the C-2 position of 11 under all conditions. Furthermore, in the absence of amine under identical open-air conditions, negligible deuterium incorporation in 11 was observed, ruling out an intramolecular [1,5]-H transfer. On the basis of these results, a deprotonation/ reprotonation mechanism was proposed to proceed through aryl anion 15. Laarhoven and co-workers have also obtained similar findings for the photocycloaromatizations of Type II-internal dienynes. 9 Key insight into the reactive excited state of the photocycloaromatization came through the work of Lewis and Sajimon who studied the reactivity of various Type II-internal dienynes with varying substitution at the terminal alkene. 10 These researchers hypothesized that the efficiency of the cyclization would increase if a higher proportion of the terminal alkene existed in the less stable syn conformation, 16-syn, versus the anti conformation, 16-anti (Table 1). To test this prediction, dienynes 16-Me and 16-cy were prepared with the expectation that 16-Me would increase the concentration of rotomer 16-syn and 16-cy would lock the dienyne in the syn conformation. As expected, the quantum yield for the formation of 17 (Φ rxn ) increased along the series 16cy > 16-Me > 16-H, but with an unexpected identical trend in

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Section: Nucleophilic Attack By the Alkynementioning

confidence: 99%

Acceleration of Conjugated Dienyne Cycloaromatization

Hitt

O’Connor

2011

Chem. Rev.

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“…Apart from diazonium salts, aryl cations have been generated only under particular conditions, viz., the irradiation of bromo - or iodobenzene in a solid argon matrix at 4 K and by solvolysis of perfluoroalkylsulfonic aryl esters 24 and of (trifluoromethanesulfonyl)oxydienynes . To our knowledge, there is no direct evidence for this elusive species in solution .…”

Section: Introductionmentioning

confidence: 95%

(Sensitized) Photolysis of Diazonium Salts as a Mild General Method for the Generation of Aryl Cations. Chemoselectivity of the Singlet and Triplet 4-Substituted Phenyl Cations

2004

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The photolysis of a series of 4-X-benzenediazonium tetrafluoroborates is studied in MeCN. Loss of nitrogen occurs from the singlet excited state with X=H, t-Bu, and NMe2 and leads to the singlet aryl cation. This adds to the solvent yielding the corresponding acetanilides. With other substituents, ISC competes with (X=Br, CN) or overcomes (X=COMe, NO2) fragmentation and the aryl cation is formed in part or completely in the triplet state. In neat MeCN, this either abstracts hydrogen from the solvent (in most cases inefficiently) or undergoes intersystem crossing to the more stable singlet that reacts as above. In the presence of pi nucleophiles (allyltrimethylsilane or benzene), the triplet aryl cation is efficiently trapped giving substituted allylbenzenes and biphenyls, respectively. By triplet sensitization by xanthone, the triplet cation and the products from it are obtained from the whole series considered. The direct or sensitized photodecomposition of diazonium fluoroborates, substituted with both electron-donating and -withdrawing substituents, in the presence of alkenes and arenes offers an access to an alternative arylation procedure.

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“…Besides 11 b, the only representative of carbocyclic hexa-1,3-dien-5-ynes ever reported is cyclodeca-1,3-dien-5-yne 11 d; its NMR structural assignment, however, is doubtful. [25,26] Experimental work on the medium-sized carbocycles 11 still has to be done to characterize this substance class more accurately. In the present study, the cycloisomerization of the Z-hexa-1,3-dien-5-yne parent system 3 to benzene 4 is discussed in detail, including all possible intermediates and transition structures.…”

Section: Introductionmentioning

confidence: 99%

The Cyclization of Parent and Cyclic Hexa-1,3-dien-5-ynes—A Combined Theoretical and Experimental Study

et al. 2001

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The thermal cycloisomerization of both parent and benzannelated hexa-1,3-dien-5-yne, as well as of carbocyclic 1,3-dien-5-ynes (ring size 7-14), was investigated by using pure density functional theory (DFT) of Becke, Lee, Yang, and Parr (BLYP) in connection with the 6-31G* basis set and the Brueckner doubles coupled-cluster approach [BCCD(T)] with the cc-pVDZ basis set for the parent system. The initial cyclization product is the allenic cyclohexa-1,2,4-triene (isobenzene), while the respective biradical is the transition structure for the enantiomerization of the two allenes. Two consecutive [1,2]-H shifts further transform isobenzene to benzene. For the benzannelated system, the energetics are quite similar and the reaction path is the same with one exception: the intermediate biradical is not a transition state but a minimum which is energetically below isonaphthalene. The cyclization of the carbocyclic 1,3-dien-5-ynes, which follows the same reaction path as the parent system, clearly depends on the ring size. Like the cyclic enediynes, the dienynes were found to cyclize to products with reduced ring strain. This is not possible for the 7- and 8-membered dienynes, as their cyclization products are also highly strained. For 9- to 11-membered carbocycles, all intermediates, transition states, and products lie energetically below the parent system; this indicates a reduced cyclization temperature. All other rings (12- to 14-membered) have higher barriers. Exploratory kinetic experiments on the recently prepared 10- to 14-membered 1,3-dien-5-ynes rings show this tendency, and 10- and 11-membered rings indeed cyclize at lower temperatures.

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Synthese und Solvolyse cyclischer Dieninyl‐triflate

Cited by 17 publications

References 13 publications

Acceleration of Conjugated Dienyne Cycloaromatization

Acceleration of Conjugated Dienyne Cycloaromatization

(Sensitized) Photolysis of Diazonium Salts as a Mild General Method for the Generation of Aryl Cations. Chemoselectivity of the Singlet and Triplet 4-Substituted Phenyl Cations

The Cyclization of Parent and Cyclic Hexa-1,3-dien-5-ynes—A Combined Theoretical and Experimental Study

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