Cycloheptadienes annulated

Transition metal (Cr, Mo) carbene complexes, e.g. 28, 30, 32, participate in additions to dienes and diene-tethered acetylenes with concomittant generation of divinyl-cyclopropanes, which undergo ring expansion under the reaction conditions to cycloheptadiene-annulated ring systems such as 29, 31 and 33. 

Vinylcyclopropylcuprates 5 were coupled with )S-haloenones giving divinylcyclopropanes 6 and 8 which rearranged to annulated or spiroannulated cycloheptadienes 7 and 9. ... 

Sealed-tube thermolysis is used to effect the rearrangement of divinylcyclopropanes such as 55, 58 and 61 to the corresponding annulated cycloheptadienes. ... 

Annulated linearly fused cycloheptadienes 6 are prepared by intramolecular cyclopropanation of dienic esters with a,) -unsaturated diazo compounds, followed by in situ rhodium-catalyzed rearrangement. ... 

Both substituted monocyclic and annulated cycloheptadienes are available by the rhodium-promoted rearrangement of divinylcyclopropanes of type 19. 

Rearrangements of divinylcyclopropanes in which one of the vinyl groups constitutes a part of an aromatic or heteroaromatic system, such as 3 or 6, are also known. The initially formed cycloheptadienes (e.g. 4) isomerizes into conjugation in those cases where a reconstitution of aromaticity results, thus providing cycloheptadienes 5 and 7, respectively, annulated with the aromatic ring. 

Davies and co-workers [12, 35] have exploited one particular aspect of the asymmetric cyclopropanation of alkenes with vinyl diazoacetates, namely, application to substrates suitable for subsequent Cope rearrangement. Cyclopropanation of dienes with predominant cfs-1,2-divinyl diastereoselection makes possible subsequent facile [3,3]-sigmatropic rearrangement with entry to 1,4-cycloheptadienes or bicyclic dienes. Two such examples employing cyclopenta-diene and penta-l,3-diene as substrates and the rhodium(II) prolinate catalyst, Rh2(2S-TBSP)4 in Fig. 1, are shown in Eq. (6) and Eq. (7),respectively cfs-l,2-di-vinylcyclopropanes are presumed to be intermediates in these annulation reactions. In contrast, ethyl diazoacetate and styrene with the prolinate catalyst (Fig. 

The reaction of vinylcaibenoids with all l-substituted acyclic dienes is an effective method for stereoselectively constructing highly functionalized cycloheptadienes. Unlike the cyclopentadiene reaction, rran -divinylcyclopropanes in addition to the [3+4] annulation products can be formed in some cases. For example, rhodium(II) acetate catalyzed decomposition of 4 in the presence of 4-methyl-l,3-pentadiene results in a 4 1 mixture of the [3+4] annulation product 17 and the tran -divinylcyclopropane 18 (Scheme 8). The regiochemistiy... 

A related [3+4] annulation between the stable chromium vinylcar-bene complex 39 and l-methoxy-3-(dimethyltert-butylsiloxy)-1,3-butadiene has been reported by Wulff and co-workers (Scheme 16). This reaction also displays poor stereoselectivity in the cyclopropana-tion step. The cycloheptadiene 40 is formed in 23% yield whereas the major product is the tranj-divinylcyclopropane 41 (40% yield). 

Barluenga and co-workers extended the scope of [3+4] annulations of chromium vinylcarbenes by using 2-amino-1,3-butadienes as the diene component. In most cases the reaction with this diene is highly diastereoselective and favors the formation of cw-divinylcyclo-propanes that rapidly rearrange to the cycloheptadienes. Furthermore, the amino functionality can be a chiral auxiliary such that an asymmetric [3+4] annulation is achieved. Examples of this approach are shown in Scheme 17. Reaction of the chromium vinylcarbene complex... 

Extension of the [3+4] annulations to more highly oxygenated dienes results in a very effective synthesis of tropones and tro-polones. For example, decomposition of the vinyldiazomethane 4 in the presence of 1-methoxy-l-trimethylsiloxy-1,3-butadiene (46) results in the formation of the cycloheptadiene 47 in 87% yield (Scheme 18). Mild hydrolysis of 47 with citric acid followed by DDQ oxidation results in a very short synthesis of the tropone 48 in 92% yield. The [3+4] annulation with 1-methoxy-l-trimethylsiloxybutadiene is applicable to a range of vinyldiazomethanes, as shown in Table 8. The major limitation is that because of the extremely electron-rich character of the diene, the formation of side products derived from zwit-terionic intermediates dominate over the [3+4] annulation. In general, the side reactions are eliminated by carrying out the reactions in a nonpolar solvent. 

The Danheiser annulation has been featured in the formal total synthesis of the natural products ( )-clavukerin (116) and ( )-isoclavukerin (117) reported by Schafer and coworkers. Cycloheptenone 118 was prepared in a three-step sequence from cycloheptadiene. Cycloheptenone 118 was then... 

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