Dienyl cyclopropanes

Diazoalkanes normally add to the terminal C-C double bonds of conjugated trienes. i, 11 e Hence diazomethane underwent addition to (Z)-hexa-l,3,5-triene to give 3-[(Z)-buta-l,3-dienyl]-4,5-dihydro-3/f-pyrazole, which yielded [(Z)-buta-l,3-dienyl]cyclopropane (44) using... 

A number of alkenylcyclopropanes have been prepared by elimination of bromide, either from a side chain or from the cyclopropane ring. The first known example is the synthesis, in 51 % yield, of (buta-l,3-dienyl)cyclopropane (2) by the reaction of(4-bromobut-l-enyl)cyclopropane (1) at 150°C with a solution of the sodium salt of 2-butylcyclohexanol in the alcohol. ... 

This method can also be applied to complexes of conjugated trienes. The uncomplexed double bond may be constructed within the complex via Wittig olefination. Cyclopropanation of the uncomplexed double bond of the resulting tricarbonyliron-triene complexes and oxidative decomplexation leads to dienylcyclopropane products. In this manner chiral dienyl-cyclopropanes 4 and 5 were prepared in high enantiomeric excess (> 90% ee) starting from optically active tricarbonyliron-hexatriene complexes 3 obtained from chirally modified sorbic aldehyde complexes. 

This strategy has been elegantly applied to the construction of rocaglamid skeleton ]62g] (Eq. 27). Numerous analogous reactions have been carried out [63-65]. The chemistry of dienyl cyclopropanes has been investigated by Oshima [64] (Eq. 28). Singleton [65] has shown that methylene cyclopentanes are obtained in good... 

Scheme 11.49 Pd(0)/dppe-catalyzed diastereoselective rearrangement of dienyl cyclopropanes hearing chiral sulfinyl group.

Fragmentation of cyclopropylcarbinyl radicals has been incorporated into several synthetic schemes.357 For example, 2-dienyl-l,l-(dimethoxycarbonyl)-cyclopropanes undergo ring expansion to cyclopentenes. 

The photoindueed 1,7-cycloaddition of carbon monoxide across the divinyl-cyclopropane derivative 32 yields the two cyclic dienyl ketones 34, via the ferracyclononadiene intermediate 33 [18]. (Scheme 11) cyclopentene rearrangement. The dienylcyclopropane 35 is capable of forming the complex 36, followed by ring enlargement to 37 [19]. 1,1-Dicyclopropylethylene 29 is also converted to the 1-cyclopropyl-1-cyclopentene 38. The additional functionality of vinylcyclopropanes is necessary to serve as a 7t-donor... 

The GIAO-MP2/TZP calculated 13C NMR chemical shifts of the cyclopropylidene substituted dienyl cation 27 show for almost all carbon positions larger deviations from the experimental shifts than the other cations 22-26. The GIAO-MP2/TZP method overestimates the influence of cr-delocalization of the positive charge into the cyclopropane subunit on the chemical shifts. Electron correlation corrections for cyclopropylidenemethyl cations such as 27 and 28 are too large to be adequately described by the GIAO-MP2 perturbation theory method and higher hierarchies of approximations such as coupled cluster models are required to rectify the problem. 

In this multi-authored monograph, several experts and leaders in the field bring the reader up to date in these various areas of research (synthesis and reactivity of zirconaaziridine derivatives, zirconocene-silene complexes, ste-reodefined dienyl zirconocenes complexes, octahedral allylic and heteroallylic zirconium complexes as catalysts for the polymerization of olefins and finally the use of zirconocene complexes for the preparation of cyclopropane derivatives). It is their expertise that will familiarize the reader with the essence of the topic. 

More recently, Hodgson et al. have found that aziridinyl anions can also undergo a diastereoselective intramolecular cyclopropanation reaction to give 2-aminohicyclo[3.1.0]hexenes in good yield <20060L995>. Reversing the addition order so that the aziridine was added dropwise to the hase led to increased yields of the hicyclic amine. When the dienyl-substituted aziridine 386 was used, an 85% yield of the 2-amino hicyclo[3.1.0]hexane 387 was obtained, which contains the potentially useful vinyl cyclopropane moiety (Scheme 98). 

In a recent development, it has been found that the cyclopropanations of electron-deficient alkenes with heteroatom-stabilized complexes, such as (la), need not be carried out with the alkene as solvent (as are the reactions in Scheme 24), but in fact better yields are obtained if the reaction is performed stoi-chiometrically in cyclohexane. A variety of different electron-deficient alkenes were examined including the dienyl ester (176) which gave a 4 1 mixture of diastereomers in 70% total yield. This report should stimulate a reconsideration of the potential of these reactions for synthetic organic applications. 

When l-diazo-3-(l-methylcyclopenta-2,4-dienyl)propan-2-one (14) was photolyzed in hexane, Wolff rearrangement occurred on direct irradiation to give 15 and intramolecular cyclopropanation on triplet-sensitized photolysis to give 16. ... 

A tandem cyclopropanation/Cope rearrangement sequence precluded the isolation of the bi-cyclic c -l,2-divinylcyclopropane9, when ( , )-hexa-2,4-dienyl 2-diazo-4-phenylbut-3-enoate and related dienylic esters were catalytically decomposed. When the double bond next to the tether had the Z configuration, however, the diastereomeric tra 5-l,2-divinylcyclopropane was formed and isolated it underwent the Cope rearrangement leading to the same product 10 only at 140 C. ... 

Using this procedure, a number of substituted cyclopropanes containing the ethenylidene or propa-1,2-dienyl group have been synthesized, with yields ranging from poor to excellent (Table 15). In the reaction of 10,10-dibromodispiro[2.0.5.1]decane, a rather complex mixture of products was obtained (see also Section 5.2.2.1.1.2.)." ... 

Cyclopropane systems can be bound to transition-metal centers either through even-numbered electron rt-bonds within the ligand (alkene, diene, alkyne) or as odd-numbered electron ligands (alkyl, allyl, dienyl). According to the bonding type, different methods of decomplexation are applied. Cyclopropane systems attached to the metal through hetero functions as n-donors are not discussed here. 

Allyl and Dienyl Transition-Metal Complexes Containing Cyclopropanes... 

The reactive intermediate generated during the course of these reactions can be applied to annulation reactions if the cyclopropane ring contains the appropriate functionalities. A suitable element is the penta-2,4-dienyl group which is attacked at the terminal position by the electrophilic cyclopropyl carbon leading to octalinone derivatives 48 and 50, respectively. ... 

Dienyl-substituted cyclopropanes 5 yield vinylcyclopentenes 6 and 7 in the presence of a catalytic amount of bis(cyclooctadiene)nickel(0) and tributylphosphane at 70... 

Allyl)-chloro-( -cyclopenta-dienyl)-dicarbonyl- 2691 Chloro-(/ -cyclopentadienyl)-dicar-bonyl-(l,2-ij -propadien)- 2691 Chloro-( -cyclopentadienyl)-cyclo-propylidene-dicarbonyl- 2691 C, H,CljNO Cyclopropane... 

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