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Cyclopentane aldehyde

Ring contractions, such as the Tavorskii reaction on (38), or the cyclopentane aldehyde synthesis on p 374... [Pg.409]

The Prins cyclization can also be coupled with a ring-contraction pinacol rearrangement, as illustrated in Scheme 1.6. This allows a smooth conversion of alkyl-idene-cyclohexane acetal 1-16 to single bond-joined cyclohexane cyclopentane aldehyde 1-17 [le]. [Pg.14]

Treatment of the chlorobenzoate 349 with potassium t-butoxide gave the cyclopentane aldehyde 350 (99) while the reduction (LiA1) of chloroketone 351 gave the cyclohexene alcohol 353 via the fragmentation of the intermediate 352 (100). [Pg.139]

Bhati et al., 1966a). The relative intensities of peaks in the mass spectra of isomeric sulphites were very different when the compounds were introduced into the ion source at 180°. However, very similar spectra were obtained when the compounds were absorbed on charcoal and introduced directly into the ion chamber at room temperature. The results were interpreted in terms of thermal loss of sulphur dioxide from the sulphites (5) to yield respectively cyclohexanone and cyclopentane aldehyde by analogy with known pyrolytic reactions (P. Brown and Djerassi, 1968). [Pg.170]

A cyclopentane aldehyde (297) is obtained when verbenone epoxide (298) is treated with zinc bromide. The presence of pinene in the products is difficult to explain, and the difference in products obtained with aluminium chloride (Vol. 1, p. 45) is remarkable. When the toluene-p-sulphonylhydrazone of the epoxide (298) is treated with potassium t-butoxide, both isomers of the cyclobutyl-acetylene (299) are obtained in an Eschenmoser fragmentation. ... [Pg.54]

A direct application of the ring-opening reaction of an epoxide by a metal enolate amide for the synthesis of a complex molecule can be found in the synthesis of the trisubstituted cyclopentane core of brefeldin A (Scheme 8.35) [68a]. For this purpose, treatment of epoxy amide 137 with excess KH in THF gave a smooth cyclization to amide 138, which was subsequently converted into the natural product. No base/solvent combination that would effect cyclization of the corresponding aldehyde or ester could be found. [Pg.296]

An allylsilane-generating CM using catalyst C between the sensitive /J-lactone 319 and allyltrimethylsilane served to introduce the allylsilane moiety in intermediate 320 as an inconsequential mixture (ca. 3 1) of (EIZ)-isomers in 80% yield. Cyclization of /J-lactone 320 with TiCl4 smoothly delivered cyclopentane 321 with inversion at the /J-carbon. Acid 321 was converted to key aldehyde 322 in three steps. The convergent fragment coupling was performed by a uniquely... [Pg.333]

A useful and simple method for the one-pot preparation of highly functionalized, enanhomerically pure cyclopentanes from readily accessible carbohydrate precursors has been designed by Chiara and coworkers [73]. The procedure depends on a samarium(II) iodide-promoted reductive dealkoxyhalogenahon of 6-desoxy-6-iodo-hexopyranosides such as 7-160 to produce a 6,e-unsaturated aldehyde which, after reductive cyclization, is trapped by an added electrophile to furnish the final product. In the presence of acetic anhydride, the four products 7-161 to 7-164 were obtained from 7-160. [Pg.523]

The inter- and intramolecular catalytic reductive couplings of alkynes and aldehydes recently have experienced rapid growth and are the topic of several recent reviews.5 h-8k 107 With respect to early transition metal catalysts, there exists a single example of the catalytic reductive cyclization of an acetylenic aldehyde, which involves the titanocene-catalyzed conversion of 77a to ethylidene cyclopentane 77b mediated by (EtO)3SiH.80 This process is restricted to terminally substituted alkyne partners (Scheme 53). [Pg.524]

The intramolecular cyclization of l,2-dien-7-ynes and l,2-dien-6-ynes regiospecifically affords the corresponding titanacycles, which react with protons, carbon monoxide, aldehydes, or imines to give single products, as shown in Eqs. 9.56 and 9.57 [102], As the formation of titanacycles and their subsequent reaction with externally added reagents such as carbon monoxide (Eq. 9.56) or an aldehyde (or imine) (Eq. 9.57) proceeds with excellent chirality transfer, this represents a new method for synthesizing optically active cyclopentane derivatives from optically active allenes [102]. [Pg.345]

The observation that fram-2-hydroxy-l-cyclopentanecarboxamide does not react with aldehydes or ketones was used in the synthesis of stereohomo-geneous cis cyclopentane-fused oxazinones and c -2-aminomethyl-l-cyclo-pentanol derivatives. The cumbersome separation of the cis- and tram-2-hydroxy-l-cyclopentanecarboxamides can be avoided, because only the cis isomer forms the oxazinone ring (81S628 83T1829). [Pg.369]

For example, rrans-2-hydroxy-l-cyclopentanecarboxamide could not be cyclized with aldehydes or ketones to the corresponding cyclopentane-fused l,3-oxazin-4-ones. This permitted a facile isomer separation (Section II,A,3). [Pg.398]

Dauben s group utilized the same retrosynthetic disconnections, but chose to add more functionality to the cycloaddition precursor. From a simple frawi-disubstituted cyclopentane, Dauben used an aldol reaction of a cyclopropylvinyl aldehyde to prepare the cycloaddition precursor. The diazo-substituted (3-ketoester was completed using a Roskamp-Padwa coupling followed by diazo-transfer. Addition of rhodium acetate to the diazo substituted p-ketoester 179 led to an excellent 86% yield of the correct diastereomer (Scheme 4.42). [Pg.281]

The reaction pathway may be supported by the observations with 4,4-dimethyl-5-trimethylsilyloxyhept-l-en-6-yne and its positional isomer 4,4-dimethyl-3-trimethylsilyloxyhept-l-en-6-yne. These react with Me2PhSiH to give the corresponding aldehydes, 280 and 282, respectively, as a mixture of two diastereomers under the conditions similar to mode 1 in Scheme 13 (Equations (47) and (48)). In the reaction of 281, an appreciable amount of 283 is formed concomitantly, which implies that the trimethylsilyloxy group at an allylic position likely retards the cyclopentane annulation step. [Pg.503]

Tomislav Rovis of Colorado State University has reported (Angew. Chem. Ini. Ed. 2005,44, 3264) the diastereoselective Lewis acid-mediated 1,3-rearrangement of dihydrooxepins such as 10 to the cyclopentene carboxaldehyde II. It is particularly convenient that the precursor aldehyde 9 is also converted into 11 under the same conditions. As there are many ways to construct alkenyl cyclopropanes such as 9 with control of both relative and absolute configuration, this is an important addition to methods for the stereocontrolled construction of cyclopentanes,... [Pg.219]

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... [Pg.181]

The photo-oxidation of n-butane has been modelled by ab initio and DFT computational methods, in which the key role of 1- and 2-butoxyl radicals was confirmed.52 These radicals, formed from the reaction of the corresponding butyl radicals with molecular oxygen, account for the formation of the major oxidation products including hydrocarbons, peroxides, aldehydes, and peroxyaldehydes. The differing behaviour of n-pentane and cyclopentane towards autoignition at 873 K has been found to depend on the relative concentrations of resonance-stabilized radicals in the reaction medium.53 The manganese-mediated oxidation of dihydroanthracene to anthracene has been reported via hydrogen atom abstraction.54 The oxidation reactions of hydrocarbon radicals and their OH adducts are reported.55... [Pg.144]


See other pages where Cyclopentane aldehyde is mentioned: [Pg.101]    [Pg.69]    [Pg.527]    [Pg.527]    [Pg.31]    [Pg.69]    [Pg.529]    [Pg.186]    [Pg.101]    [Pg.69]    [Pg.527]    [Pg.527]    [Pg.31]    [Pg.69]    [Pg.529]    [Pg.186]    [Pg.181]    [Pg.157]    [Pg.6]    [Pg.73]    [Pg.116]    [Pg.61]    [Pg.240]    [Pg.12]    [Pg.247]    [Pg.343]    [Pg.334]    [Pg.839]    [Pg.15]    [Pg.18]    [Pg.1055]    [Pg.635]    [Pg.441]    [Pg.1165]    [Pg.214]    [Pg.255]    [Pg.482]    [Pg.161]    [Pg.365]   
See also in sourсe #XX -- [ Pg.36 ]




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