1-Cyclopentene-1-carboxaldehydes

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,... 

Valerianine (13) was synthesized in racemic form by Franck and coworkers (75) in 1970. Diene condensation of 5-methyl-l-cyclopentene carboxaldehyde (175) with 1,3-dimethoxy propene (176) afforded the tetrahydropyranyl ether 177, which, on acid hydrolysis, afforded 9-methoxy-iridodial (178). This compound was not isolated, but was converted directly to ( )-valerianine 13) with either Fe(NH4)2S04 or NH2OH (Scheme 8)... 

Cyclopentene-l-carboxaldehydes are obtained from cyclohexene precursors by the sequence cyclohexene - cyclohexane-1,2-diol -> open-chain dialdehyde - cyclopentane aldol. The main advantage of this ring contraction procedure is, that the regio-and stereoselectivity of the Diels-Alder synthesis of cyclohexene derivatives can be transferred to cyclopentane synthesis (G. Stork, 1953 G. BUchi, 1968). 

Scheme 9 [3+2] Cycloaddition of nitrones with 1-cyclopentene-l-carboxaldehyde...

The synthesis of iV-substituted-S -trimethylenepyrazoles (45) from iminophosphoranes and 2-azido-l-cyclopentene-l-carboxaldehyde has been described (R = Ph, CH2Ph, CH2C02Et) (88S742). 

The fluorescence quantum yields of pyrene-1-carboxaldehyde in water and methanol are 0.98 and 0.07/ an effect attributed to solvent effects on 7c,n and n,n states. Cycloaddition reactions of 1-naphthonitrile to 1,2-dimethyl-cyclopentene are attributed to both and Lj, states.It is pointed out that although dual fluorescence is known, this is the first example of divergent reaction from two nearly isoenergetic singlet states. An analysis of the u.v. spectra of some acyl pyridines, including a theoretical examination of the molecular geometry, and excited states of bipyrimidine compounds have also been made. Photo tautomerism and the fluorescence of the cation of 4-amino-pyrazole[3,4-iflpyrimidine, an analogue of adenine, has been published by Wierzchowski et Intramolecular heteroexcimer formation in... 

Preparation of a compound such as 3 is useful where extensive functionalization of a cyclic enone is required. In addition to 3, 4,4-dimethyl-3-hydroxy-l-cyclopentene-l-carboxaldehyde was prepared using the same... 

Cyclamen homoaldehyde Cyclohexanone, 4-[(3,3-dimethylbicyclo [2.2.1] hept-2-yl) methyl]-2-methyl- 4-Cyclohexyl-4-methylpentan-2-one 3-Cyclopentene-1 -acetonitrile, 2,2,3-trimethyl- Decahydro-2,8,8-trimethylnaphthalene-2,4a-carbolactone trans-4-Decenal Dihydroisojasmone Dihydroterpinyl acetate Dimethyl bicycle [2.2.1] heptane-2-carbonitrile 1,5-Dimethylbicyclo [3.2.1] octan-8-one oxime 2,4-Dimethyl-3-cyclohexene carboxaldehyde Dimethyl-3-cyclohexene carboxaldehyde 1,3-Dimethyl-3-phenylbutylacetate 2,2-Dimethyl-3-phenylpropanol 4-Ethyl-a,a-dimethyl benzenepropanal 2-Ethyl-4-(2,2,3-trimethyl-3-cyclopenten-1-yl)-2-buten-1-ol Geranyl nitrile... 

More complex branching occurs in mechanisms where selectivities arise. Therefore, consider as an example the overall transformation of a symmetric alkene cyclopentene in the presence of CO and H2 to both cyclopentane carboxaldehyde and cyclopentane, facilitated by the addition of a Group 9 (or CAS systems VIIIB) metal hydride complex HML capable of performing both hydroformylation [27,28] and hydrogenation [29]. Upon addition of the metal hydride to the system, one would expect the steps HML —> HML i —> H(ji-cyclopentene)ML i CsH9ML i where the bold intermediates should be common to both unicycUc catalytic sequence of steps. At this point there is a branching in the network of intermediates, and one of either two paths is followed ... 

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