Cyclopropane ring, fused

Nucleosides such as 178 and 179 containing a cyclopropane ring fused to the sugar portion have shown antiviral activity their stereocontrolled syntheses have recently been achieved, Eq. (69) [233]. 

A cyclopropane ring fused to a further ring as in 245 has proved to be a particularly apposite substrate for the detection of the so-called halolithiocarbenoids such as 246 (this compound is formed from the geminal dibromide with n-butyl lithium). At — 100°C in... 

Abstraction of bromine from a cyclopropane ring fused to another ring gives variable amounts of alkenylcyclopropanes, depending on the size of the second ring. Thus, reaction of 7-bro-mobicyclo[4.1.0]heptane (7) with potassium tert-butoxide in dimethylsulfoxide gave a 24% yield of bicyclo[4.1.0]hept-2-ene (8) (see also Section 5.2.2.1.1.2.). 

Zeise s dimmer ([Pt(C2H4)Cl2]2 (21.5 mg, 0.0366 mmol) was dissolved in 5 mL CH2CI2 under an atmosphere of nitrogen. The solution was then transferred by syringe to a flask containing 1.0 mmol cyclopropane ring-fused sugar and 2.0 mmol benzyl alcohol. The... 

Otherwise, the leaving group may be in the homoallylic situation either in the glycal itself or on a branch carbon atom in both situations the double-bond electrons of the glycal bond to the homoallylic carbon atom to give products with cyclopropane rings fused to furanoid or pyranoid rings, respectively. In this way compounds 76 [105] and 77 [106] are converted to cyclopropa-furanoid and -pyranoid nucleosides (Schemes 25 and 26, respectively). 

Several tricyclic compounds exist in nature with a cyclopropane ring fused to a cw-decalin structure, as shown in the molecule tricyclo[5.4.0 . 0 ]undecane (below). In various countries, some of these substances have a history of use as folk medicines for purposes such as contraception. Make a model of this compound. How does the cyclopropane ring affect the conformations of the two cyclohexane rings The cyclohexane rings in cw-decalin itself are capable of (simultaneous) chair-chair interconversion (recall Exercise 4-13). Is the same true in tricyclo[5.4.0. 0 ]undecane ... 

The structures of bicyclic and polycyclic small-ring compounds have attracted some interest. The relationship between the C-C-H bond angles at the bridgehead of bicyclo[1.1.0]butane (2) and the angle between its cyclopropane rings has been studied.31 Bicyclobutane and most other cyclopropane derivatives have bonds that are formed from orbitals that are bent in the same direction. However, with some mm -fused bicyclic compounds containing a cyclopropane... 

Lower temperatures are enough with a strong Lewis acid like Et2AlCl. The cyclopropane 52 comes from available dihydrofuran 50 by rhodium-catalysed carbene insertion. Rearrangement at very low temperatures gives the cyclopentene 53 that actually has three five-membered rings fused together.13... 

Given the rich variety of electron transfer induced reactions observed for cyclopropane systems, it is not surprising to find a similarly rich reactivity for systems comprised of two fused cyclopropane rings. For bicyclobutane systems, such as the trimethyl derivative (71), nucleophilic capture leads to addition with cleavage of the transannular bond (->72). Alternatively, the initial capture and ring opening may be accompanied by dehydrogenation (—>73) [246],... 

Another interesting transformation of alcohols was effected using bicyclic 1-alkanols with a fused cyclopropane ring, which were cleaved oxidatively to alkenoic acids [131] ... 

The acid-catalyzed cyclization of appropriate aryloxyketones formed benzo[l,2-6 5,4-6 ]difuran and benzo[ 1,2-6 4,5-6 ]difuran (63BSF1003). Another variation involved the cyclization of an aryl thioacetal to a benzo[l,2-6 4,5-6 ]dithiophene <86CB3198>. In investigations of the synthesis of a unit of the CC-1065 skeleton (see Section 7.21.12), a carbene derived from the azo-compound (59) constructed the cyclopropano-fused benzodipyrrole (60) by simultaneous formation of the heterocyclic ring and the cyclopropane ring <83TL4773>. 

During the course of this project, over 600 new compounds with anti-aldoster-one activity were synthetized. Some of these has a fused cyclopropane ring in place of a double bond because of the known electronic similarity under certain circumstances. The test models were developed and the anti-aldosterone activity tests were performed by Losert and coworkers [7]. Sex hormone activity investigations were conducted at Schering s endocrine pharmacology unit, and spirorenone (6/ ,7/ 15/ ,16/ -dimethylen-3-oxo-17a-pregna-l,4-dien-21,17-carbolac-tone) (Fig. 17.4) [3,8] was finally chosen as the candidate for development. 

Finally, we describe the two syntheses of [3]peristylane 403) reported by Garratt and White.369 This hydrocarbon is constructed of three cyclopentane rings which are mutually fused in a manner which also generates a cyclopropane ring. Subsequent to the conversion of norbomadiene to endo-3-carboxybicyclo[3.2.1 ]oct-6-ene 401) by an established route,370 this acid was reduced and reoxidized to the aldehyde level (Scheme 65). Pyrolysis of the sodium salt of the corresponding tosyl-... 

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