Cyclo procedure

It is tempting to envisage use of the cyclo procedure also for very simple parent systems, above all when special relationships could thus be expressed by the name itself, e.g. ... 

Selecting the naphtha type can be an important processing procedure. For example, a paraffinic-base naphtha is a better feedstock for steam cracking units because paraffins are cracked at relatively lower temperatures than cycloparaffins. Alternately, a naphtha rich in cycloparaffins would be a better feedstock to catalytic reforming units because cyclo-paraffins are easily dehydrogenated to aromatic compounds. Table 2-5 is a typical analysis of naphtha from two crude oil types. 

The reaction described is of general synthetic utility for the preparation of a variety of cyclic /3-keto esters from the corresponding ketones. Using this procedure the 2-carbethoxy-cycloalkanones have been prepared from cyclononanone, cyclo-decanone, and cyclododecanone in yields of 85%, 95%, and 90%, respectively. The procedure is simpler and gives much higher yields than other synthetic routes to these systems. 

Butvlcyclohexanone by Conjugate Addition of a Chiral Hetcrocuprate Derived from C to 2-Cyclo-hexenone (Table 4, Entry 9) Typical Procedure ... 

A one-pot procedure [9] based on the cycloaddition of 4-aryl-2-silyloxybuta-dienes 7 and bisdiene 8 with alkynes, followed by oxidative aromatization of the cycloadducts, opened a route to polycyclic phenols without isolating the cyclo-hexadiene derivative intermediates (Scheme 2.5). 

To obtain reliable chromatograms in the final step of the determination of the analytes by LC or GC, it is important to remove interfering signals resulting from coelution of other compounds. To this end, a variety of techniques are applied for cleanup of the sample extract. The most effective procedures for sample cleanup for PAH measurements are partitioning between M, N-dimethylformamide/water/cyclo-hexane and LC on silica and on Sephadex LH 20. Other cleanup procedures include LC on alumina or XAD-2 and preparative thin-layer chromatography. 

The same reaction sequence may be used to convert cyclo-dodecanone to cyclotetradecanone. Preparation of the pyrrolidine enamine of cyclododecanone requires 2-3 days at reflux, and reaction of the enamine with methyl propiolate is best carried out in refluxing hexane. The enamine-propiolate reaction may also be used to convert cycloheptanone to cyclononanone. In this case the procedure must be modified to provide for partial hydrogenation of the intermediate amino ester without prior hydrolysis.8 The reduced intermediate is saponified as described in the present procedure. 

Schafer and coworkers devised a useful synthetic procedure based on this reaction [26]. Thus, the Diels-Alder reaction of /i-silylacrylic acid with cyclo-pentadiene gave the adduct which was oxidized anodically with the elimination of the carboxyl and the silyl groups. Successful formation of norbonadiene indicates that /J-silylacrylic acid can be used an a synthon of acetylene in Diels-Alder reactions with dienes (Scheme 33). 

Preparation.—From Halogenophosphine and Organometallic Reagents. The cyclo-pentadienylphosphines (1) have been obtained from the reaction of cyclopenta-dienylthallium with chlorophosphines in ether.1 Diphenyl(4-pyridyl)phosphine (2) is prepared from 4-pyridyl-lithium and chlorodiphenylphosphine,2 and an improved procedure for the synthesis of tri-(2-pyridyl)phosphine (3) from 2-pyridyl-lithium and phosphorus trichloride has been reported.3... 

Bicyclo[4.3.0]nonenes, thanks to their frequent appearance in natural products, are other important targets for novel annulation methodology. A six-membered ring-annulation to cyclopentenones has yet to be developed, the main reason for this being that, until very recently, the levels of enantioselectivity in catalytic 1,4-additions to 2-cyclopentenone were too low for a synthetically useful procedure. However, a highly enantioselective annulation of a five-membered ring to 2-cyclo-hexenone has been developed (Scheme 7.26) [80]. 

The growth step procedures for the cycloaddition reaction are very simple. Combination of an ethynyl-substituted dendrimer and an excess of the cyclo-pentadienone in a refluxing solvent such as o-xylene, diphenylether, or methyl-naphthalene (with b.p. higher than 130 °C) typically results in quantitative conversion within 24 h. The refluxing of the solvent is necessary to accelerate the elimination of the carbon monoxide in the cycloaddition. The purity of the resulting compounds was checked by MALDI-TOF mass spectrometry which showed quantitative reaction, facilitating work-up. By repeated precipitation in methanol, the pure product can be isolated as white amorphous powders in yields higher than 90%. 

Synthetic equivalents of 1,4-cyclohexadiene, such as 1,3-cyclohexadiene or 3-bromocyclohexene, have also been used for the preparation of 1. The procedure is generally applicable to linearly fused cydoproparenes such as IFf-cyclo-propa[b]naphthalene (42), and many even highly strained cydoproparenes... 

The automatic procedure for reference spectra generation was first demonstrated for the start-up of a homogeneous catalyzed rhodium hydroformylation of cyclo-octene using Rh4(CO)i2 as precursor, n-hexane as solvent and FTIR as the in situ spectroscopy at 298 K [63]. The first n spectra were (i) empty spectrometer compartment (background), (ii) n-hexane at 0.2 MPa in a high pressure thermostatically controlled cell fitted with Cap2 windows (iii) system equilibrated with 2.0 MPa CO, (iv) system upon addition of cyclo-octene, and (v) system upon addition of Rh4(CO)i2. The n=l reference spectrum, which contained atmospheric... 

The synthesis of bis(rj8-cyclooctatetraene)uranium(IV) (uranocene)J from uranium tetrachloride and (cyclooctatetraene)dipotassium was first published in 1968.1 The method reported here is a modification of that procedure and is suitable for a large variety of cyclooctatefraene complexes.2-4 BisO 8-cyclo-octatetraene)uranium(IV) has also been prepared by the reaction of uranium tetrafluoride with (cyclooctatetraene)magnesium in the absence of solvent.5 Direct reaction of finely divided uranium metal with cyclooctatetraene vapors at 150° also gives some uranocene.5 However, both methods give low yields. 

Tropolone has been made from 1,2-cycloheptanedione by bromination and reduction, and by reaction with N-bromosuccinimide from cyclo-heptanone by bromination, hydrolysis, and reduction from diethyl pimelate by acyloin condensation and bromination from cyclo-heptatriene by permanganate oxidation from 3,5-dihydroxybenzoic acid by a multistep synthesis from 2,3-dimethoxybenzoic acid by a multistep synthesis from tropone by chlorination and hydrolysis, by amination with hydrazine and hydrolysis, or by photooxidation followed by reduction with thiourea from cyclopentadiene and tetra-fluoroethylene and from cyclopentadiene and dichloroketene. - The present procedure, based on the last method, is relatively simple and uses inexpensive starting materials. Step A exemplifies the 2 + 2 cycloaddition of dichloroketene to an olefin, " and the specific oycloadduot obtained has proved to be a useful intermediate in other syntheses. " Step B has been the subject of several mechanistic studies, " and its yield has been greatly improved by the isolation technique described above. This synthesis has also been extended to the preparation of various tropolone derivatives. - " ... 

Izumiya and co-workers (77JA8346) have undertaken a systematic study of the chiral induction on hydrogenation (H2,l atm., Pd black, MeOH) of a series of cyclodipeptides of the type cyclo(L-aminoacyl-Dha), where Dha represents dehydroalanine. These were synthesized from the corresponding L-serine derivatives the final dehydration was accomplished by Photaki s procedure (63JA1123). Contrary to the report of the earlier workers, the de in the product cyclo(L-aminoacyl-Ala) [(S,S) over (S,R) was the highest with valine (98.4%) and the least with proline (84.8%). Leucine gave about 95% de. 

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