Preparation and reactions of some 2,2-difunctional 1,1-dibromocyclopropanes (original) (raw)
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Conversion of some dihalogenocyclopropanes into unsaturated ketones
Journal of the Chemical Society C: Organic, 1977
ABSTRACT Dibromocyclopropanes, prepared by addition of dibromocarbene to cyclic olefins, give unsaturated ketones, with ring expansion, when treated with silver sulphate in concentrated sulphuric acid at room temperature. Mild hydrogenation of a dibromocyclopropane gave equivalent amounts of the monobromocyclopropane and of a ring-opened bromine-free compound.
Some Reactions of gem -Dibromocyclopropanes and Metal Carbonyls
Journal of the Chinese Chemical Society, 2012
A series of gem-dibromocyclopropanes were treated with various metal complexes. Among the metal complexes, Ru(CO) 2 (PPh 3) 3 , Ru(CO) 3 (PPh 3) 2 , and Mo(CO) 6 were able to remove a bromine atom from 1,1-dibromo-2-phenylcyclopropanes (1) to yield a series of corresponding of 1-bromo-2-phenylcyclopropanes (2). Upon the treatment of 1 with Cr(CO) 6 in DMSO, a series of allenes were obtained in good yields. The correlation between the rate of formation of allenes and the substituents on the benzene gives a negative coefficient which suggests the dibromocyclopropanes possesses as an electrophile toward to Cr(CO) 6. In the presence of Cr(CO) 6 , gem-dibromobicyclo[n,1,0]alkanes (4) in DMF or DMSO solution underwent the cleavage of carbon-bromine bond followed by ring-expansion and coupling reaction to form bicycloalkenes 7.
Stereochemistry of two new polyfunctionalizedgem-dihalocyclopropanes
Acta Crystallographica Section C Crystal Structure Communications, 2002
The two new gem-dihalogenocyclopropanes (1 H S,3R)-3-(2 H ,2 Hdichloro-1 H-methylcyclopropyl)-6-oxoheptanoic acid, C 11 H 16-Cl 2 O 3 , (2), and (1 H S,3R)-3-(2 H ,2 H-dibromo-1 H-methylcyclopropyl)-6-oxoheptanoic acid, C 11 H 16 Br 2 O 3 , (3), are isostructural. Both present two stereogenic centers at C1 H and C3. The absolute con®guration was determined by X-ray methods. The cyclopropyl rings are unsymmetrical, the shortest bond being distal with respect to the alkyl-substituted C atom. Comment Despite their high ring strain, cyclopropanes are commonly encountered among both naturally occurring and synthetic compounds. In addition, diastereoselectively substituted cyclopropanes have attracted attention as useful precursors of highly strained molecules (Boche et al., 1990; Tanabe et al., 1996) and biologically active pyrethroids (Hirota et al., 1996; Kunzer et al., 1996). Thus, the promise of their usefulness as synthetic intermediates is growing rapidly. We describe here the structure of two new polyfunctionalized dichloro and dibromo cyclopropanes, (2) and (3), which could be valuable synthons for pyrethroid derivatives.
Arkivoc, 2008
Selected members of the title family of compounds, prepared from 1,1-dibromo-2-chloro-2diethoxymethylcyclopropane by standard chemical transformations, were dissolved in mixtures of dichloromethane and a protic, nucleophilic reagent and treated with 50% aqueous sodium hydroxide in the presence of a phase-transfer catalyst, triethylbenzylammonium chloride (TEBA), at room temperature. In all cases except two, regiospecific ring opening of the cyclopropane took place, giving one product formed by nucleophilic attack of the carbon atom to which the polar substituent was attached. This clearly lends support to the notion that hydrogen bonding contributes significantly to direct the attack of protic nucleophiles.
Use of Cyclopropanes and Their Derivatives in Organic Synthesis
Under the influence of a variety of chemic- reagents (e.g., electrophiles, nucleophiles, radicals) or external physical forces (e.g., heat, light), cyclopropane deriva- tives undergo a variety of ring-opening reactions. In contrast to normal paraffins, the chemistry of the cy- clopropane C-C single bond resembles that of a car- bon-carbon double bond. Relief of ring strain provides a potent thermodynamic driving force for these pro- cesses. Since numerous methodologies have been de- veloped for the construction of three-membered car- bocycles, the chemistry of cyclopropanes has emerged as a versatile tool in organic synthesis. In this section, the theoretical basis for the “unusual”reactivity and properties of cyclopropane is reviewed.