Cyclynes. 7. Homoconjugated cyclic poly(diacetylene)s

Scott, Lawrence T.; Cooney, Mark J.; Johnels, Dan

doi:10.1021/ja00166a061

Cited by 60 publications

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Metal alkynyl complexes are currently of great interest [1,2] since they are valuable for constructing vinylidene or carbene complexes for use in organic synthesis. [3±8] Reactions of organotransition metal halides with 1-alkynes in the presence of anions such as PF 6 À , BF 4 À , and CF 3 SO 3 À are representative methods for the preparation of vinylidene complexes.

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mentioning

confidence: 99%

Unprecedented Formation of Five-, Six-, and Seven-Membered Metallacycles by Single and Double Insertion of Mono- and Disubstituted Alkynes into an Rh−O Bond

Yamamoto

Xiao-hong

2000

Angew. Chem. Int. Ed.

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confidence: 99%

Unprecedented Formation of Five-, Six-, and Seven-Membered Metallacycles by Single and Double Insertion of Mono- and Disubstituted Alkynes into an Rh−O Bond

Yamamoto

Xiao-hong

2000

Angew. Chem. Int. Ed.

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“…In seeking neutral and mild conditions, it was found that Scott and coworkers described a modified Cadiot-Chodkiewicz conditions for the synthesis of polydiacetylenes by coupling separately prepared copper(I) acetylides with bromoalkynes in pyridine. [50] With slight modifications to these conditions, A 2 PA 1 was converted to its Cu acetylide by the continuous addition of an excess amount of CuCl in degassed DMF at room temperature over 5 min, followed by quenching with a solution of an excess amount of phenylethynyl iodide in degassed pyridine (Scheme 2c), thereby affording 8 in 52 % overall yield based on A 2 PA 1. The same protocol can be used a second time on compound 8 to afford the bis-butadiyne-substituted phosphaalkene 9 (Scheme 2d).…”

Section: Resultsmentioning

confidence: 99%

Acetylene‐Expanded Dendralene Segments with Exotopic Phosphaalkene Units

Geng

Ott

2011

Chemistry A European J

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Bis-TMS protected C,C-diacetylenic phosphaalkene (A(2)PA) 1 (Mes*P=C(C≡CTMS)(2); Mes* = 2,4,6-tBu(3)Ph) has been used as a building block for the construction of butadiyne-expanded dendralene fragments in which phosphaalkenes feature as exotopic double bonds. Treatment of 1 with CuCl gives rise to a Cu(I) acetylide that is selectively formed at the acetylene trans to the Mes* group. The cis-TMS-acetylene engages in similar chemistry, albeit at higher temperatures and longer reaction times. The differentiation between the two acetylene termini of 1 allows for the controlled synthesis of the title compounds by a variety of different Cu- and Pd-catalyzed oxidative acetylene homo- and heterocoupling protocols. Crystallographic characterization of A(2)PA 1 and dimeric Mes*P=C(C≡CR(1))C(4)(R(2) C≡C)C=PMes* (3b, R(1) = R(2) = Ph; 6, R(1) = R(2) = TMS), and 10 (R(1) = R(2) = C≡CPh) verifies that the stereochemistry across the P=C bond is conserved during the coupling reactions, whereas spectroscopic evidence reveals cis/trans isomerization in an iodo-substituted A(2)PA intermediate 4 (Mes*P=C(C≡CTMS)(C≡CI). UV/Vis spectroscopic and electrochemical studies reveal that efficient π conjugation operates through the entire acetylenic phosphaalkene framework, even in the cross-conjugated dimeric structures. The P centers contribute considerably to the frontier molecular orbitals of the compounds, thereby leading to smaller HOMO-LUMO gaps than in all-carbon-based congeners. Phenyl- and/or ethynylphenyl substituents at the A(2)PA framework influence the HOMO and LUMO to a varying degree depending on their relationship to the Mes* group, thus enabling a fine-tuning of the frontier molecular orbitals of the compounds.

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“…1,1-Bis(trimethylsilylethynyl)cyclopropane (4) was prepared in 91% yield from the known 1-(bromoethynyl)-1-(trimethylsilylethynyl)cyclopropane (7) [4] by simple lithiation followed by quenching with trimethylsilyl chloride (Scheme 1). The diester 5 was prepared in 74% overall yield from 1,1-diethynylcyclopropane (3) by double deprotonation with n-butyllithium, carboxylation of the intermediate dilithiodiacetylene with carbon dioxide, and esterification with methanol according to the Kabada procedure.…”

Section: Resultsmentioning

confidence: 99%

“…[1] The question of its ability to transmit electronic effects has also been probed with various model compounds [2] including the perspirocyclopropanated pericyclines (1b) [3] and the so-called expanded [n]rotanes (2b), [4] in comparison with the ''pericyclines'' (1a) [5,6] and ''expanded pericyclines'' (2a). [7,8] The numerous arguments, for and against homoconjugation and homoaromaticity in these cycles have been reviewed. [8] One of the most serious arguments against is found in the similarities in the energetic properties of 1b (n ϭ 1) (calculated at the B3LYP/D95d/B3LYP/6-31G* level of theory) [3b] and 2b (n ϭ 2) (calculated at the AM1 level of theory) [4b] to those of the parent 1,1-diethynylcyclopropane (3).…”

Section: Introductionmentioning

confidence: 99%

Structural Parameters and Electronic Interactions in Substituted 1,1-Diethynylcyclopropanes − An Experimental Study

Meijere

Kozhushkov

Boese³

et al. 2002

Eur. J. Org. Chem.

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Keywords: Alkynes / Conjugation / Diethynylcyclopropanes / Small ring systems / Structure elucidation 1,1-Bis(trimethylsilylethynyl)cyclopropane (4) and dimethyl 3,3Ј-(1,1-cyclopropanediyl)bis(2-propynoate) (5) have been prepared by silylation of the known 1-(bromoethynyl)-1-(trimethylsilylethynyl)cyclopropane (7) and by double carboxylation of 1,1-diethynylcyclopropane (3) followed by esterification, in 91 and 74% overall yields, respectively. 7,7-Diethynyldispiro[2.0.2.1]heptane (6) has been synthesized from ethyl dispiro[2.0.2.1]heptane-7-carboxylate (9) by a ten-step sequence in 41% overall yield. Upon UV irradiation, the diacetylene 4 underwent ethylene extrusion, and the resulting bis(trimethylsilylethynyl)carbene dimerized with electron reorganization to give 1,4,8-tris(trimethylsilyl)-3-(trimethylsilylethynyl)oct-3-ene-1,5,7-triyne (20) (24% yield). X-ray crystal structure analyses of 4, 5, and 6 revealed strong electronic

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Cyclynes. 7. Homoconjugated cyclic poly(diacetylene)s

Cited by 60 publications

References 0 publications

Unprecedented Formation of Five-, Six-, and Seven-Membered Metallacycles by Single and Double Insertion of Mono- and Disubstituted Alkynes into an Rh−O Bond

Unprecedented Formation of Five-, Six-, and Seven-Membered Metallacycles by Single and Double Insertion of Mono- and Disubstituted Alkynes into an Rh−O Bond

Acetylene‐Expanded Dendralene Segments with Exotopic Phosphaalkene Units

Structural Parameters and Electronic Interactions in Substituted 1,1-Diethynylcyclopropanes − An Experimental Study

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