General approach to the synthesis of polyquinenes. VIII. Synthesis of triquinacene, 1,10-dimethyltriquinacene, and 1,10-cyclohexanotriquinacene

Abstract

The synthesis of tricyclo[5.2.1.01 234'10]deca-2,5,8-triene (1), 1,10-dimethyltricyclo[5.2.1.04,1°]deca-2,5,8-triene (3), and tetracyclo[5.5.2.01,8.04,8]tetradeca-2,5,13-triene (4) has been accomplished via the reaction of 1,2-dicarbonyl compounds with di-zerz-butyl 3-oxoglutarate (Weiss reaction). Condensation of glyoxal 5a with di-rerZ-butyl 3-oxoglutarate (6b) gave the tetra-te/7-butyl w-dioxobicyclo[3.3.0]octane-2,4,6,8-tetracarboxylate 7b in 93% yield. This bisenol 7b was converted into the bisenol ether 9b regios pecifically (90% yield). This transformation was followed by monoalkylation (KH, allyl iodide; -58 °C) and hydrolysis to generate 2-allyl-n4-bicyclo[3.3.0]octane-3,7-dione in 90% overall yield from 9b. The mixture of epimeric 2-allyl-3,7-diones 11a,b was transformed (03; DMS) into the mixture of epimeric aldehydes 12a,b. This process was followed by aldol cyclization (2 N HC1, THF) to provide the diastereomeric mixture of endo-(13a) and exo-(13b) triquinane monols in 85% yield. Reduction of 13a,b with borane-THF (0 °C) generated the stereoisomeric mixture of triols 14a,b which were subjected to an HMPA-mediated dehydration sequence to provide triquinacene (1), accompanied by small amounts of isotriquinacene. The mixture of trienes were converted into pure 1 by exposure to p-TSA in methylene chloride-pentane. Substitution of biacetyl (5b) for glyoxal 5a in the Weiss reaction, followed by the analogous steps detailed in the synthesis of 1, provided 1,10-dimethyltriquinacene (3). In addition, the synthesis of 1,10-cyclohexanotriquinacene (4), another centro-substituted triquinacene, has been accomplished by substitution of cyclohexane-1,2-dione (23) for 5a in the condensation, followed by the same sequence of reactions presented above for 1 and 3.

From Fragmentation to Construction—from Void to Massive: Fascination with Organic Mass Spectrometry and the Synthesis of Novel Three‐Dimensional Polycyclic Aromatic Hydrocarbons

“…The chemistry of the polyquinanes was described in several impressive surveys, such as Trost's[88] and Paquette's[89,90] review articles, the research towards dodecahedrane by Paquette[91] and Prinzbach[92] was highly impressive, and Greenberg and Liebman had published their inspiring book on strained organic molecules [93]. A number of groups, including Deslongchamps et al.,[94] Jacobson,[95] de Meijere et al.,[96] Cook et al [97]. and Serratosa et al [98].…”

Three-Dimensional Hydrocarbon Cores Based on Multiply Fused Cyclopentane and Indane Units: Centropolyindanes

“…Development of propellane chemistry since Ginsburg's pioneering work comprised various studies on [3.3.3]propellanes . A particular impact has been the first synthesis of triquinacene reported by Woodward et al, which triggered several longstanding efforts to provide improved syntheses of this prototypical triquinane tris(homotriene), − understand its electronic nature, − and perform its dimerization to pentagon−dodecahedrane, the latter goal having never been achieved. ,,,,− Other outstanding landmarks in this field of polyquinanes and polyquinenes were the successful syntheses of the parent all- cis -[5.5.5.5]fenestrane (“staurane”) − and the related all- cis -[5.5.5.5]fenestra-2,5,8,11-tetraene and related staurane derivatives. − The most prominent motif for research into fenestranes has been the challenge to flatten (“planarize”) the geometry of the central, tetracoordinate carbon atom. − Important variants of this theme comprised small-ring congeners, which have become experimentally accessible down to [4.4.4.5]fenestranes in the all- cis series − but also include the highly strained cis , cis , cis , trans stereoisomers of different ring sizes. − …”

Divergent Synthesis of Antiviral Diterpenes Wickerols A and B

“…Hydroborationoxidation of terminal olefin 13 and subsequent oxidation with Dess−Martin periodinane delivered aldehyde 15 in 78% yield. Treatment of 15 with 6 N HCl effected the desired intramolecular aldol reaction, 22 giving 16 as a single diastereomer, which was likely the result of a steric interaction with the axial C14-methyl group. Notably, subjecting 15 to basic conditions ( t BuOK, tetrahydrofuran) led to the formation of retro-Michael addition product 4 in 20% yield, in addition to 16 in 42% yield (not shown).…”