The Synthesis of [2.2]Phanes

Vögtle, Fritz; Neumann, Peter R.

doi:10.1055/s-1973-22137

Cited by 110 publications

(42 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For instance, by adding a tenfold excess of lithium powder to a solution of 3 in dry THF at 0 °C we obtained only compound 4, in 25% isolated yield, along with some intractable material (Scheme 2). 16 Si(i-Pr) 3 Si(i-Pr) 3 (i-Pr) 3 …”

Section: Methodsmentioning

confidence: 99%

Reduction of Pseudo-geminal Bis(ethynyl)-Substituted [2.2]Paracyclophanes

Sarbu¹,

Hopf²,

Grunenberg³

et al. 2014

Synlett

View full text Add to dashboard Cite

The reduction of pseudo-geminal bis(ethynyl)-substituted [2.2]paracyclophanes provides compounds with new bridges. The type of bridging is substituent dependent. The (trimethylsilyl)ethynyl moiety induces the formation of a bridge with two semicyclic double bonds; less bulky substituents, like propynyl and phenylethynyl, lead to bridges with endo double bonds.Key words acetylenes, reduction, dienes, lithium, paracyclophanes [2.2]Paracyclophane derivatives have been the subject of particular interest since their first appearance in the literature more than six decades ago.1-3 Since then, most studies have been devoted to elucidation of the structural characteristics of [2.2]paracyclophanes, particularly their geometry and steric properties, transanular interactions, and ring strain. [4][5][6] As far as the chemical behavior is concerned the vast majority of the reported reactions has been carried out at the benzene rings. The chemistry of the molecular bridges of these molecules should also be interesting, especially when the bridges carry important functional groups. In the last several years we have developed several methods for the introduction of new bridges into [2.2]paracyclophanes. 7 Although we reported the incorporation of various functional groups into the ethano bridges of [2.2]paracyclophanes, 8 the chemistry of this type of bridge has received little attention so far.Functional groups in pseudo-geminally substituted [2.2]paracyclophanes often undergo highly specific reactions. This is due to the rigid framework and the short distance within the aromatic units. In one such application, unsaturated cyclophane bis(esters) provided the corresponding ladderanes by intramolecular photocyclization. 9-11The 4,13-bis(ethynyl)[2.2]paracyclophane and its derivatives are interesting building blocks for molecular scaffolding, 12 since the ethynyl functions can easily be connected by various coupling reactions.Pentalenes represent another class of hydrocarbons with an impressive chemical history. 13 The development of the chemistry of these antiaromatic 4n hydrocarbons was strongly correlated with the number of efficient synthetic methods for the preparation of these compounds. A general route to dibenzopentalenes is represented by the metal-induced dimerization of different types of ethynyl aromatics. 14 For example, the reduction of tris(isopropyl)silylethynylbenzene (1) with excess lithium, followed by oxidation with iodine provided the dibenzo[a,e]pentalene derivative 2 in 7% yield (Scheme 1). 15 Scheme 1Prompted by these recent developments on the chemistry of pentalenes, we decided to investigate the reactions of a series of pseudo-geminally substituted bis(ethynyl) derivatives with lithium. Thus, we are presenting here a preliminary report on the interaction of lithium with 4,13-bis(trimethylsilyl)-, 4,13-bis(propyn-1-yl)-, and 4,13-bis(phenylethynyl)[2.2]paracyclophanes.In a first experiment we have used as substrate an ethynyl aromatic compound related to 1, 4,13-bis(trimethylsilyl)[2.2]paracyclo...

show abstract

Section: Methodsmentioning

confidence: 99%

Reduction of Pseudo-geminal Bis(ethynyl)-Substituted [2.2]Paracyclophanes

Sarbu¹,

Hopf²,

Grunenberg³

et al. 2014

Synlett

View full text Add to dashboard Cite

show abstract

“…[28][29][30][31][32][33] On the other hand, aromatic hydrogens of anti-4a appear at slightly low field than that of syn-4b and syn-4c. The tert-butyl protons were also observed higher field at δ 1.03, 1.12 ppm for compound 4b and δ 1.08 ppm for compound 4c, compared to that of analogue anti-5a and anti-5b at δ 1.27 and 1.36 ppm due to the strong shielding effect of the benzene ring.…”

Section: Resultsmentioning

confidence: 99%

“…2, bottom), it seen that the two benzene ring are closest face to face and due to ring current the aromatic protons are shielded to high field at δ 1.08 ppm ( ppm for the protons of the aromatic rings due to shielded by the adjacent ring, a common consequence of a face-to-face benzene ring. [28][29][30][31][32][33] The tert-butyl protons for compounds syn-6b were observed at higher field at δ 1.10 and 1.14 ppm compared to those of the anti-7b at δ 1.22 and 1.27 ppm due to the shielding effect of the benzene ring. These observations strongly suggest that compound 6b adopts syn-conformation.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and conformational studies of 9-benzyloxy-18-substituted [3.3]metacyclophanes

et al. 2015

View full text Add to dashboard Cite

A series of syn- [3.3]metacyclophanes (MCPs) containing internal substituted benzyloxy group have been synthesized by the modified TosMIC coupling reaction, followed by acid treatment and Wolff-Kishner reduction. anti-Mono-and di-benzyloxy[3.3]MCPs are synthesized by Obenzylation of the corresponding hydroxy[3.3]MCPs, which are obtained by demethylation of methoxy[3.3]MCPs with BBr 3 at room temperature. An interesting and intriguing result was obtained when syn -6,15-di-tert-butyl-9-methoxy-18-methyl[3.3]MCP-2,11-dione was treated with TMSI afforded to form dihydrobenzofuran ring by nucleophilic intramolecular cyclization reaction. The 1 H NMR and X-ray analysis of 6a confirms that it adopts syn (chair-chair) conformation in both solution and solid state.

show abstract

“…The 1 H NMR spectrum (in CDCl 3 ) of anti-4d exhibits two sets of doublets at = 3.28, 3.76 ppm (J = 15.0 Hz) and = 3.40, 3.45 ppm (J = 13.2 Hz) for the ArCH 2 COCH 2 Ar methylene protons and a singlet for the internal methoxy group at an = 3.36 ppm from anisole ( = 3.75 ppm) due to the ring current of the opposing aromatic ring. [26][27][28][33][34][35][36][37][38] Similarly, the internal aromatic proton at 18-position was 5.39 ppm compared to that of the 3b at 7.28 ppm. These observations strongly suggest that compound anti-4d adopts the anti-conformation.…”

Section: Resultsmentioning

confidence: 99%