Triquinacene derivatives

Oxidative cleavage of the organic fragment from the metal is possible using Ce and gives the tricyclic rearrangement product (34) in very high yields (equation 15) 45,46 The tetranitrile, (34), prepared in this manner has been used as a key intermediate in the synthesis of chiral 2-substituted triquinacene derivatives.51... 

The intramolecular version presents a very useful synthetic route to various polycyclic compounds. Even terminal alkenes give cyclopentenones in good yields, assisted by the addition of /V-methylmorpholine N-oxide (NMO) [85], The addition of trimethylamine A -oxidc also dramatically accelerates the reaction in the presence of oxygen, and both inter- and intramolecular reactions proceed at 0°C to room temperature [86]. The reaction was found to proceed rapidly at 25 °C by the addition of aqueous NH4OH [87]. Numerous applications to natural product syntheses have been reported. The tri- and tetracyclic skeletons 214 for crinipellin B, from 213 [88], and the triquinacene derivative 216, from 215, have been constructed [89,90], These results show that internal alkynes and terminal alkenes react smoothly in the intramolecular reactions. Domino reaction of the endiyne 217 produced the strained molecule of oxa[5.5.5.5]fenestrenedione (219) via 218 [91]. 

Hydrocarbon 400, a triquinacene derivative as well as a member of the [12]-annulene family, has also been prepared (Scheme 64).367 Benzotricyclo-... 

Similar intramolecular cycloadditions of cyclic alkenes containing alkynyl substitution have been explored by Serratosa in the 3-(3-butynyl)cyclopentene series. The product in this case is a triquinacene derivative, a tricyclo[S.2.1.0 - 0](ig( ane. Since the targets in Serratosa s studies required functionalization of all three five-membered rings, all cycloaddition substrates utilized contained varying degrees of sub-... 

Various triquinacene derivatives 2, i.e. molecules containing a bicyclo[3.3.0]octa-2,7-diene moiety with an additional linkage between C4 and C6, undergo the same type of reaction either on sensitized or direct irradiation giving bicyclo[2.1.0]pentanes 3. - ... 

The scope of the intramolecular Pauson-Khand has been rapidly expanded as both more complex and heteroatom-containing substrates have been employed. Cycloadditions involving a cycloalkene reaction partner afford the direct construction of tricyclic systems in a single step. Triquinacene derivatives are efficiently obtained from 3-(3-butynyl)cyclopentenes [Eq. (55)]. An unusual characteristic of this system is the epimerization that occurs at the pro-pargylic position subsequent to cobalt complexation but prior to cyclization. The steric demands on the reaction are evidently so large that one stereoisomer is unable to cyclize and, instead, isomerizes through a cobalt-stabilized propargylic cation [123]. 

Scheme 10.10 outlines Deslongchamps synthesis of triquinacene derivatives. Manipulation of Thiele s acid (146) gave the key product, 147. A photochemical fragmentation gave 148. and an intramolecular aldol... 

Paquette (1974) has used a 1,3-cycIoaddition reaction followed by oxidative removal of the tricarbonyliron group in a ready preparation of triquinacene derivatives from cyclooctatetraene [Eq. (59)]. 

The absolute configuration of (-f )-2,3-dihydrotriquinacen-2-one, and of its tetra-hydro-derivative, have been established as 15 by chiroptical measurements of the long wavelength n-n transitions. The Py-double bond is a dominant chiroptical feature of this triquinacene derivative, and the positive Cotton effect of the enhanced n-Ti transition is consistent with the absolute configurational assignment indicated by (9 RR = O). These are the first members of the triquinacene family for which... 

Upon exposure to Heck-type reaction conditions, a triquinacene derivative was shown to react with iodobenzene in a process that led to the introduction of a phenyl group at the central (and sp -hybridized) carbon of the tricyclic ring system (eq 125). ... 

Cadieux JA, Buller DJ, Wilson PD (2003) Versatile route to centro-substituted triquinacene derivatives synthesis of 10-phenyltriquinacene. Org Lett 5 3983-3986... 

Provide the structure of the triquinacene derivative that could be prepared from cyclohexan-l,2-dione using this strategy. (Unnatural Products-13)... 

Some illustrative examples from the field of polyquinanes are the synthesis of some derivatives of bicyclo[3.3.0]octane 6 (Scheme 6.7) [12] [15] -which have been used in the total syntheses of coriolin, hirsutic acid and quadrone- and the synthesis of triquinacene 7 and some of its derivatives. The retrosynthetic analysis of perhydrotriquinacene-l,4,7-trione (7a) is shown in Scheme 6.7bis. In the actual synthesis the hydroxy groups must be protected either as trialkylsilyl ethers or more conveniently as benzyl ethers [16] [17]. 

An alternative practical synthesis of triquinacene-2-carboxylic acid (as the dextrorotatory enantiomer) has l n described by Deslongchamps and Soucy Their protocol begins with hydroxy ketone 467 and passes via the 2-methyl derivative (Scheme XXXVIII). Selenium dioxide oxidation of the hydrocarbon provided the aldehyde which was further oxidized and then hydrolyzed to arrive at the add. 

Following resolution with (—)-quinine, (+)-465 was transformed into the (-l->2-formamido derivative which was condensed with the acid chloride of (+)-465 to give the secondary amide 468. From this point, the cyclic imidate salt 469 was prepared, but cyclization to the dodecahedrane nucleus could not be realired With Thiele s add as starting material, several routes to triquinacene and 2,3-dihydrotriquinacen-2-one 462) have been developed Triquinacene reacts with Mo(CO)g to give tricarbonyl(triquinacene)molybdenum (470) and with (CHjCI -... 

The (non-combustion calorimetrically) experimentally determined enthalpies of formation for benzvalene [31], semibullvalene [32], and triquinacene [33] are 363, 308, and 224 kJ mol1 respectively. Assuming linear dependence of enthalpy of formation on any of these counts (r2 = 0.98), we derive a value for the enthalpy of formation of tetrahedrane of 437 kJ mol1. The equivalent non-statistical derivation is to assume thermoneutrality for the reaction... 

Serratosa has critically evaluated the various entries to the triquinacene system available via Pauson-Khand chemistry, concluding that a route involving cycloaddition of the dibenzylated enyne substrate (Schemes 17 and 23) is operationally the simplest for preparation of multigram quantities of tricy-clo[5.2.1.0 °]decane-2,5,8-trione. This in turn is a key intermediate for the study of synthetic entries to dodecahedrane and its derivatives. An optically active version of this synthesis has l n developed as... 

The bis(trimethylstannyl) derivative of triquinacene, which can be regarded as a bis(tri-allylstannane), was used for preparing the triquinacene dianion (equation 22-5).22 A secondary benzyl system provides an exception to the rule that the transmetallations involve configurational retention.23... 

Centropolyindanes constitute a complete family of arylaliphatic polycyclic hydrocarbons containing several indane units. Mutual fusion of the five-membered rings leads to three-dimensional, carbon-rich molecular frameworks bearing a central carbon atom, such as benzo-annelated [3.3.3]propellanes, triquinacenes, and [5.5.5.6]- and [5.5.5.5]fenestranes. In this review, the structural concept of centropolyindanes is contrasted to other fused indane hydrocarbons. Besides the syntheses of the parent centropolyindanes and recently described related indane hydrocarbons, the preparation of a large variety of bridgehead and arene substituted centropolyindanes is presented including strained, heterocyclic, and centrohexacyclic derivatives. In appropriate cases, the particular reactivity and some structural features of these unusual, sterically rigid polycyclic compounds are pointed out. 

Substituted cw-trishomobenzene derivatives have been prepared and found to give the monocyclic triene rapidly. But perhaps the most spectacular example is that of the methane-capped material, diademane, which gives triquinacene with log k = 14.6 - 31600/2.3/ r (Scheme 10.69). 

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