Diels‐Alder‐Addukte des 1,7‐Dehydroquadricyclans

Abstract

Nach Einwirkung von sperrigen Lithiumamiden auf 1-Chlorquadricyclan in Gegenwart von Anthracen, 9-Methoxyanthracen, 2,5-Dimethylfuran, Furan oder 1,2,3-Trimethylisoindol isolierte man die entsprechenden Diels-Alder-Addukte des 1,7-Dehydroquadricyclans 4a, 4 b, 8a, 10 und 17 in befriedigenden bis guten Ausbeuten. Die Konstitution von 4a wurde durch Rontgenstrukturanalyse gesichert. Versuche zur lsomerisierung des Quadricyclan-Teils der Addukte zu der entsprechenden Norbornadien-Einheit lieferten nur polymeres Material. Thiophenol addierte sich selektiv an die zentrale Propellan-Bindung von 4a zum Thioether 28a. Acetylendicarbonsauredimethylester und Azodicarbonsaure-diethylester reagierten am Quadricyclan-System von 17 unter Bildung der Bruckenkopfolefine 24 und 25. Diels-Alder Adducts of 1,7-DehydroquadricyclaneThe reaction of bulky lithium amides and 1-chloroquadricyclane in the presence of anthracene, 9-methoxyanthracene, 2,5-dimethylfuran, furan, and 1,2,3-trimethyIisoindole afforded the corresponding Diels-Alder adducts of 1,7-dehydroquadricyclane 4a, 4 b, 8a, 10 and 17 in satisfactory to good yields. The structure of 4a has been established by x-ray analysis. Attempts to isomerize the quadricyclane parts of the adducts to the corresponding norbornadiene units led only to polymeric material. Thiophenol selectively cleaved the central propellane bond of 4a to give the thioether 28a. Dimethyl acetylenedicarboxylate and diethyl azodicarboxylate reacted with the quadricyclane system of 17 leading to the bridgehead olefins 24 and 25. Der nucleophile Austausch des Chlorids gegen den Butylrest im I-Chlorquadricyclan(1) durch n-Butyllithium vollzieht sich iiber einen Eliminierungs-Additions-Mechanismus3) mit 1,7-Dehydroquadricyclan (2) und 1,5-Dehydroquadricyclan (3) als reaktiven Zwischenstufen. Cycloadditionen dieser kurzlebigen, pyramidalisierten Bruckenkopfolefine4' sollten ihre Existenz weiter festigen. Wir konnten das I ,7-Dehydroquadricyclan (2) in der Tat mit einigen 1,3-Dienen in Diels-Alder-Reaktionen abfangen.

Thermal Isomerization of 12‐Oxa‐1,9‐dimetylhexacyclo[7.2.1.02,4.02,8.03,7.06,8]dodec‐10‐ene: A Computational Mechanistic Investigation

“…The volatile material was condensed in a dry-ice/acetone-cooled trap. 2,4-Dimethyl-3-oxahexacyclo[5.5.0.0 1,10 .0 2,6 .0 4,10 .0 5,9 ]-dodec-11-ene (9a; 250 mg, 83%) was isolated as the sole product, besides some minor impurities (NMR) of unknown structure. 4 ) The structure of 9a was established by INADEQUATE NMR experiments.…”

“…The recovery of the material amounted to 83%. After removal of some polymeric material, NMR analysis showed that no starting material was present and that 2,4-dimethyl-3-oxahexacyclo[5.5.0.0 1,10 .0 2,6 .0 4,10 .0 5,9 ]dodec-11-ene (9a) had been formed as the sole product.…”

Experiments Towards the Formation of 1,6-Dehydroquadricyclane and Density Functional Calculations on This and Related Molecules

“…The that of 21e with the exception of the signal for C-6 which appeared at δ ϭ 15.26 as a low intensity triplet. 2,7 .0 4,6 ]heptane (21f): Compound 6 (1.08 g, 4.32 mmol) Photocyclization of 24c: Compound 24c (100 mg, 0.480 mmol) in ether (10 ml) was mixed at Ϫ78°C with tBuLi (5.40 ml, 8.64 was irradiated in 15 ml of ether with a mercury high-pressure lamp mmol). The pale yellow solution was stirred for 1 h at Ϫ78°C and at Ϫ12°C for 24 h in the presence of acetophenone (2.88 mg, 0.0240 charged with chlorotrimethylsilane (428 mg, 3.94 mmol).…”

“…After removal of the volatile products in vacuo, 23c (78.0 ture was allowed to warm to room temperature and hydrolyzed mg, 78%) was isolated as a colorless oil. 2,7 .0 4,6 ]heptane (23a): Compound 6 (1.30 g, 5.20 mmol) in ether (8.0 ml) was mixed at solvent removed in vacuo from a 0°C bath. According to NMR…”

“…gave rise to 1,6-dilithioLithium halide elimination has proved as an efficient method for the generation of strained olefins [2] and hydrocarbons [3] . This reaction has furnished evidence for the formation of 1,7-dehydroquadricyclane (1) [4] [5] , 1,5-dehydroquadricyclane (2) [6] and 1,2-dehydroquadricyclane (3) [7] , which could be trapped as Diels-Alder adducts. Ab initio MO calculations at the TCSCF level of theory using the 6-31G* basis set showed that 1, 2, and 3 were local energy minima on the C 7 H 6 energy hypersurface, as was the nonolefinic 1,6-dehydroquadricyclane (4) [7] .…”