Cyclopropanation of Vinylidenecyclopropanes. Synthesis of 1-(Dihalomethylene)spiropentanes (original) (raw)
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Journal of chemical research, 2017
Cyclopropanes are one of the most important strained small ring cyclic hydrocarbons that have attracted much attention. 1,2 Multicomponent reactions can be an ideal way for the preparation of cyclopropanes, in which one-pot transformations take place to yield the final product. 3-5 Cyclopropanes are one of the most important and fundamental groups in many naturally occurring compounds and pharmaceutical and agrochemical products. 6,7 Moreover, they exhibit a wide range of biological activity 8 ranging from enzyme inhibition to antibiotic, herbicidal, antitumor, 9 anticancer, 10 antibacterial, antiviral, antimycotic, antineoplastic, antimetastatic, thyromimetic, anti-HIV, phytotoxic, and insecticidal activities, as well as carboxy peptidase inhibition properties 11 and antiviral properties. 12 In this study, we planned to prepare some cyclopropane compounds for bio-testing. We were guided in our choice of method by some recent work by Bavantula and co-workers 13 in which a series of polysubstituted cyclopropane compounds were prepared in a highly stereoselective way. The synthesis involved the reaction between 4-chlorophenacylpyridinium bromide (prepared in situ from the reaction between pyridine and 4-chlorophenacyl bromide) and indan-1,3-dione and an araldehyde in the presence of trimethylamine in acetonitrile. It occurred to us that an interesting series of related polycyclic cyclopropane compounds could be formed by using most of the same reactants under similar conditions but replacing 4-chlorophenacylpyridinium bromide with acetopyridinium chloride. Here we report on the successful synthesis of a series of six novel cyclopropane compounds.
ChemInform Abstract: Glycosylidene Carbenes. Part 3. Synthesis of Spirocyclopropanes
ChemInform, 2010
ChemInform Abstract The phenols (II) are treated with compounds such as (I) and (V) in order to elucidate the influence of the acidity of phenols on the yields, diastereoselectivity and regioselectivity of their glycosidation. It is shown, that differences in the kinetic acidities of glycosyl acceptors possessing more than one OH-group serve as the basis for a regioselective reaction which does not require protective groups (cf. (I) → (-)-(VIII) + (+)-(IX)) and that steric hindrance is relative unimportant for the synthesis of glucosides (cf. reaction of I) with (X)). O-Aryl glycosides possess a variety of biological activities.
Journal of the American Chemical Society, 1993
2,2-Dichloro-or 2,2-dibromovinylcyclopropane was condensed with electron-deficient alkenes in a phenylthio radical catalyzed process to afford 4-substituted and 4,5-disubstitutedl,l-dihalo-3-vinylcyclopentane derivatives in good yield and with good-to-excellent diastereoselectivity for the 3,4-cis isomer. Neither electron-rich nor p-substituted alkenes led to good yields of cyclopentane products. The diastereoselectivity and reactivity profiles of these transformations are satisfactorily rationalized by application of existing transition-state models of radical reactions. Our studies of the phenylthio radical catalyzed [3-atom + 2-atoml addition of substituted vinylcyclopropanes (or vinyloxiranes) with two-atom unsaturated addends (eq 1) havedetailed 1 3 many of the salient regiochemical and stereochemical features of this transformation which, in turn, define its scope and limitations for complex molecule synthesis.'.* Specifically, the all-carbon series (X, A, B = carbon substituents) has proven to be particularly versatile for the synthesis of a wide range of functionalized vinylcyclopentane derivatives with moderate levels ofstereoselectivity.1b-f In addition toprovidng access tosubstituted vinylcyclopentanes, these studies have helped illuminate the scope and magnitude of the critical steric interactions which, when taken together, determine the stereochemical outcome of cyclization of the putative intermediate 5-hexenyl radical 4. With ' 4d / 48 4b 4c one significant exception, the prevailing dogma' provides adequate rationalization for these observations. This exception arises upon consideration of the origins of 1,3 anti stereochemistry in product 3 upon cyclization of 4. Houk3a.b and Beckwith" have, independently, developed computational models based on parameter sets derived from simple, unadorned substrates which suggest that the boat-like/equatorial-R transition-state model 4c is a
Convenient synthesis of new functionalized cyclopropanes from monoterpenic olefines
Arkivoc, 2006
Five new cyclopropyl-ketoacids were prepared in good yields from monoterpenic olefines using solid-liquid phase transfer catalysis (SL-PTC) dichlorocyclopropanation reaction followed by oxidative cleavage with RuCl 3 -NaIO 4 system. The nonchlorinated cyclopropanes were obtained by sodium/methanol reduction of the corresponding gem-dichlorocyclopropanes.
Simple Approach to the Highly Stereoselective Synthesis oftrans-1,2-Cyclopropane Derivatives
Chinese Journal of Chemistry, 2007
In the presence of KF•2H 2 O, furoylmethyltriphenylarsonium bromide (1a) or thienoylmethyltriphenylarsonium bromide (1b) reacted with 2-[(un)substituted benzylidene]malononitrile (2) in chloroform at room temperature to give trans-3,3-dicyano-1-furoyl-2- [(un)substituted phenyl]cyclopropane (3a) or trans-3,3-dicyano-1-thienoyl-2-[(un)substituted phenyl]cyclopropane (3b) respectively in good yield with high stereoselectivity. The structures of product 3 were confirmed by IR, MS, 1 H NMR, 1 H-1 H COSY and microanalysis. The relative configuration of product 3 was determined by 1 H-1 H NOESY technique. The mechanism for the formation of product 3 was also proposed.
Synthesis of Spiro[2.2]pentanes and Spiro[2.3]hexanes Employing the Me3 Al/CH2 I2 Reagent
European Journal of Organic Chemistry, 2017
Substituted alkylidenecyclopropanes reacted with 5 equivalents each of Me3Al and CH2I2 at room temperature in hexane to give 1-mono-and 1,1-disubstituted spiro[2.2]pentanes in high yields. Surprisingly, the same reaction with substituted alkylidenecyclopropanes in CH2Cl2 afforded exclusively 1,1disubstituted spiro[2.3]hexanes. The transformation of 1,1diphenylspiro[2.2]pentane into 1,1-diphenylspiro[2.3]hexane was studied with the use of CD2I2 and a plausible mechanism was suggested. The reaction of substituted alkylidenecyclobutanes with the Me3Al/CH2I2 reagent in CH2Cl2 gave only 1,1-disubstituted spiro[2.3]hexanes.
Rh-Catalyzed rearrangement of vinylcyclopropane to 1, 3-diene units attached to N-heterocycles
2011
Summary Dienes embedded in quinolizidine and indolizidine structures can be prepared in four steps from cyclic nitrones and bicyclopropylidene. The key intermediates α-spirocyclopropanated N-heterocyclic ketones, generated via a domino 1, 3-dipolar cycloaddition/thermal rearrangement sequence, were converted by Wittig methylenation to the corresponding vinylcyclopropanes (VCPs), which underwent rearrangement to 1, 3-dienes in the presence of the Wilkinson Rh (I) complex under microwave heating.