Cyclopentane 1,2 Dimethyl cyclopropane

Rhodium(II) acetate catalyzes C—H insertion, olefin addition, heteroatom-H insertion, and ylide formation of a-diazocarbonyls via a rhodium carbenoid species (144—147). Intramolecular cyclopentane formation via C—H insertion occurs with retention of stereochemistry (143). Chiral rhodium (TT) carboxamides catalyze enantioselective cyclopropanation and intramolecular C—N insertions of CC-diazoketones (148). Other reactions catalyzed by rhodium complexes include double-bond migration (140), hydrogenation of aromatic aldehydes and ketones to hydrocarbons (150), homologation of esters (151), carbonylation of formaldehyde (152) and amines (140), reductive carbonylation of dimethyl ether or methyl acetate to 1,1-diacetoxy ethane (153), decarbonylation of aldehydes (140), water gas shift reaction (69,154), C—C skeletal rearrangements (132,140), oxidation of olefins to ketones (155) and aldehydes (156), and oxidation of substituted anthracenes to anthraquinones (157). Rhodium-catalyzed hydrosilation of olefins, alkynes, carbonyls, alcohols, and imines is facile and may also be accomplished enantioselectively (140). Rhodium complexes are moderately active alkene and alkyne polymerization catalysts (140). In some cases polymer-supported versions of homogeneous rhodium catalysts have improved activity, compared to their homogenous counterparts. This is the case for the conversion of alkenes direcdy to alcohols under oxo conditions by rhodium—amine polymer catalysts... 

Radical iodine atom transfer [3 + 2]-cycloaddition with alkene (118) using dimethyl 2-(iodomethyl)cyclopropane-l,l-dicarboxylate (117) forms cyclopentane derivative (119), through the formation of an electron-deficient homoallyl radical, followed by the addition to alkene, and cyclization via 5-exo-trig manner as shown in eq. 4.41. 

Cyclobutan 2-Oxo-l-(2-oxo-phenyl-ethyl)- E17e, 307 [1-SAr-1 -(CH = CH — CO — Ar) — cyclopropan-Umlager.] Cyclobutene l,2-Dimethyl-3-hydroxy-4-oxo-3-phenyl- E17f, 1012 (Oxo -> OH/Ar) Cyclopentan l-Benzoyl-2-oxo-Vl/ld, 66... 

Cyclopentan 4,5-Dimethyl-3-methoxy-3-methylthio-l, 1,2,2-tetracyan- E17c, 2156 (1-OR— 1-SR-2,3-R2-cyclopropan +... 

Cyclohexen ( + )-l-Acetoxy-2,6-dimethyl-6-ethoxycarbonyl-E15/1, 76 (Keton + R-COOH) Cyclopentan 2-(3-Ethoxy-allyl)-2-ethoxycarbonyl-l-oxo- E15/1. 295 (Claisen-Umlager.) Cyclopropan 2,3-Diethoxycarbonyl-l-(2-methyl-l-propenyl)- E17a, 237 (subst. Cyclopropen + ROOC en-COOR) E18, 891 (Cyclopropen 4- En) 5,8-Dioxa-spiro 3.4 oct-l-en 2-Butyl-(or tert.-ButyI)-1 -isopropyloxy-3-oxo- E17f, 805 [l,2-(OR)j —4 OSiRj — 4-R — 3-oxo —cyclobuten + l,2-(OSiR3)2 — ethan] Ethan 1,1-Diethoxy-2-(4-methoxy-phenoxy)- E6b/1, 94 f, [OH -> 0-CH2-CH(0R)2]... 

Pyrolysis of 4,5-dihydro-3//-pyrazole (3) at 223 °C gave an 89% yield of cyclopropane. In a similar manner, 2-(aminomethyl)cyclopentan-l-amine gave 2,3-diazabicyclo[3.3.0]oct-2-ene yield 80% bp 73.5 C/14Torr. On photolysis, this gave bicyclo[3.1.0]hexane in 68% yield. 2,2-Dimethylpropane-l, 3-diamine gave 4,4-dimethyl-4,5-dihydro-3//-pyrazole yield 65% bp 66-67°C/40Torr. Pyrolysis at 249°C gave a 97% yield of 1,1-dimethylcyclopropane. 

The selectivity for the alkene-substituted cycloadduct is also almost complete in the case of the reaction of l-methylene-2-(trimethylsilyl)cyclopropane (5) with dimethyl fumarate, which results in a 78% yield of dimethyl /ra x-4-(trimethylsilylmethylene)cyclopentane-l,2-di-carboxylate (7). Interestingly, only one of the stereoisomeric dimethyl 4-methylene-3-(trimethyl-silyl)cyclopentane-l,2-dicarboxylates [the (/ , / , / )-isomer 8] is formed selectively. ... 

This reaction was first reported by Perkin in 1883. It is the nucleophilic alkylation between malonic ester and Q, o)-alkyl dihalide to form cyclic aliphatic 1,1-diester or acid and is known as the Perkin reaction or Perkin synthesis. Although it was once referred to as the Perkin condensation, this name should not be used for this type of reaction. Using this protocol, Perkin successfully prepared cyclopropane-, cyclobutane-, cyclopentane-, cyclohexane-, and cycloheptane-1,1-dicarboxylie acids. However, this reaction is often complicated by the side reaction that forms Q, o, a ,a -tetracarboxylic ester from the Sn2 reaction between malonic ester and o, a -alkyl dihalide, this side reaction can be depressed if alcoholic sodium malonic ester is added slowly to the o, a -alkyl dihalide with vigorous stirring. It is interesting that the K2CO3 promoted a reaction between dimethyl 1,3-acetonedicarboxylate and tran5 -l,4-dibromobutene yields vinyldihydrofuran. ... 

As an example of the use of this methodology in total synthesis, the zirconocene-promoted ring contraction was the key step in the route to (+)-epiafricanol (100) reported by Paquette et al. [78]. Vinyl pyranose 95, obtained from D-glucose in 12 steps, was treated with Cp2Zr in toluene at -78°C and then with boron trifluoride etherate at room temperature, affording vinyl cyclopentane 96 in a 63% yield. Conversion of 96 to ketone 97 with periodinane as the oxidant in the presence of sodium bicarbonate and addition of the lithium derivative to 4,4-dimethyl-5-iodo-l-pentene 98 gave rise to 99. Cyclization of 99 by RCM followed by cyclopropanation finally afforded the desired product 100 (Scheme 3.39). 

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