Kondensierte Ringsysteme, XVI. Synthese, Kristall‐ und Molekularstruktur eines 1,4‐überbrückten Dewar‐Benzols der [6.2.2]Propellanreihe mit Konformationsenantiomerie

Weinges, Klaus; Kasel, Wolfgang; Huber‐Patz, U.; Rodewald, H.; Irngartinger, Hermann

doi:10.1002/cber.19841170514

Cited by 16 publications

(2 citation statements)

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“…Molecular Modeling. The SYBYL-minimized Dewar pyrimidinone subunit was found to be quite similar in structure to two crystal structures of Dewar valence isomers (Weinges et al, 1984 and). The 117°f lap angle (angle between the two mean planes of the four-membered rings) of TpT3 compares quite favorably with that of 116-117°found in the crystal structures.…”

Section: Discussionmentioning

confidence: 65%

Solution-state structure of the Dewar pyrimidinone photoproduct of thymidylyl-(3' .fwdarw. 5')-thymidine

Taylor

Garrett²,

Cohrs³

1988

Biochemistry

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The preparation, spectroscopic investigation, structure determination, conformational analysis, and modeling of the Dewar pyrimidinone photoproduct of thymidylyl-(3'----5')-thymidine, previously referred to as TpT3 [Johns, H. E., Pearson, M. L., LeBlanc, J. C., & Heilleiner, C. W. (1964) J. Mol. Biol. 9, 503-524], is described. TpT3 was prepared in quantitative yield by photolysis of an aqueous solution of the (6-4) photoproduct of TpT with Pyrex-filtered medium-pressure mercury arc light. TpT3 was analyzed by FAB MS, IR, UV, and 1H, 13C, and 31P NMR spectroscopy. The spectroscopic data led to the conclusion that TpT3 results from the photoisomerization of the pyrimidinone ring of the (6-4) product of TpT to its Dewar valence isomer. Torsion angle and interproton distance information derived from coupling constants and NOE data was used to constrain ring conformation searches by utilizing the SYBYL molecular modeling program subroutine SEARCH. Sets of angles derived from the ring search procedure were then used to construct structures whose geometries were optimized by the energy-minimization subroutine MAXIMIN. A two-state model for the solution-state structure of the Dewar photoproduct was chosen which was energetically sound, fit the experimental coupling constants with an RMS deviation of 1.15 Hz, and was consistent with the NOE data. The model for the Dewar photoproduct was compared to a model for the (6-4) photoproduct and the TpT subunits of the Dickerson dodecamer structure by a least-squares fitting procedure. It was concluded that the Dewar photoproduct more closely resembles a B-form TpT unit than does the (6-4) photoproduct.

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Section: Discussionmentioning

confidence: 65%

Solution-state structure of the Dewar pyrimidinone photoproduct of thymidylyl-(3' .fwdarw. 5')-thymidine

Taylor

Garrett²,

Cohrs³

1988

Biochemistry

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“…In the 1970s and 1980s some thiapropellanes were utilised in the preparation of Dewar benzene systems [2][3][4][5], in some cases the crystal structures of the Dewar benzene-containing propellanes were also determined [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Structural and theoretical study on the 1:2 addition complex of 1,2,4,5-bis{8′,11′-dithia[4.3.3]propella(3′,4′)}benzene with I2

Szlachcic

Seidler

Stadnicka

2013

Journal of Molecular Structure

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The Ramberg‐Bäcklund Reaction

Taylor

Casy

2003

Organic Reactions

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The base‐mediated conversion of alpha‐halosulfones into region‐defined alkenes was first described by Ludwig Ramberg and Birger Backlund. This transformation has proved to be of wide synthetic value and is known as the Ramberg‐Backlund reaction (RBR). The facile nature of the RBR is surprising given the difficulties encountered when attempting to carry out nucleophilic substitution reactions on alpha‐halosulfones. In contrast to halogens adjacent to carbonyls and related electron‐withdrawing groups, polar, steric and field effects appear to combine leading to the marked deactivation of alpha‐halosulfones. The stereochemical outcome of the reaction was also unexpected: a predominance of Z‐alkenes is often observed with relatively weak bases, whereas stronger bases tend to favor E‐alkenes. The mechanism of the RBR was therefore the subject of intense interest, particularly in the 1950s and 1960s. From the synthetic viewpoint, the RBR is attractive for a number of reasons, for example, the accessibility of the precursor sulfide and sulfones; the conjunctive nature of the process; the unambiguous location of the resulting double bonds, among others. Organic sulfones are readily available, but the preparation of alpha‐halosulfones can be problematic. In view of this, perhaps the most significant synthetic advance concerning RBR has been the development of Meyer's modification, which involves in‐situ halogenation‐RBR sequence and enables sulfones to be converted directly into alkenes. This chapter discusses the mechanism of RBR, its scope and limitations, applications of the reaction in natural product synthesis, and comparison of the RBR with related procedures. Representative experimental procedures are also given.

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Kondensierte Ringsysteme, XVI. Synthese, Kristall‐ und Molekularstruktur eines 1,4‐überbrückten Dewar‐Benzols der [6.2.2]Propellanreihe mit Konformationsenantiomerie

Cited by 16 publications

References 10 publications

Solution-state structure of the Dewar pyrimidinone photoproduct of thymidylyl-(3' .fwdarw. 5')-thymidine

Solution-state structure of the Dewar pyrimidinone photoproduct of thymidylyl-(3' .fwdarw. 5')-thymidine

Structural and theoretical study on the 1:2 addition complex of 1,2,4,5-bis{8′,11′-dithia[4.3.3]propella(3′,4′)}benzene with I2

The Ramberg‐Bäcklund Reaction

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