Cyclo converters

Voltage source inverter (VSl) using IGBTs 6/125 Current source inverter (CSl) 6/126 Cyclo converters (frequency converters) 6/127 The regenerative schemes 6/127... 

In addition to the above inverter systems there is one more system, called a cyclo converter system. These drives tire employed for very large motors, when IGBTs in such ratings are a limitation. It converts the fixed a.c. supply frequency to a variable frequency, generally lower than rated, directly and without rectifying it to a d.c, source. They are basically frequency converters. This system is more complex and expensive and has only... 

Power eonverter terminology can be confusing. Traditionally, a.c. to d.c. converters were referred to as rectifiers, d.c. to a.c. converters as inverters, d.c. to d.c. converters as ehoppers, a.c. to a.c. (at same frequency) as a.c. power controllers, and a.e. to a.e. (at dilferent frequencies) as cyclo-converters [26]. Power eleetronie systems often eombine multiple conversion processes and are often simply referred to as converters or power-conditioning systems. 

The PdCli-catalyzed instantaneous rearrangement of A -carbethoxy-S-azabi-cyclo[5.1.0]oct-3-ene (60) takes place at room temperature to give A -car-bethoxy-8-azabicyclo[3.2.1]oct-2-ene (61)[50], The azepine 62 undergoes a smooth skeletal rearrangement to give 63, and the diazepine 64 is converted into the open-chain product[51]. Beckmann fission of the oxime 65 of ketones and aldehydes to give the nitrile 66 is induced by a Pd(0) complex and oxygen [52,53]. 

DimeriZa.tlon. A special case of the [2 + 2] cyclo additions is the dimerization of ketenes. Of the six possible isomeric stmctures, only the 1,3-cyclobutanediones and the 2-oxetanones (P-lactones) are usually formed. Ketene itself gives predominandy (80—90%) the lactone dimer, 4-methylene-2-oxetanone (3), called diketene [674-82-8], approximately 5% is converted to the symmetrical dimer, 1,3-cyclobutanedione [15506-53-3] (4) which undergoes enol-acetylation to so-called triketene [38425-52-4] (5) (44). 

Protonated pyridazine is attacked by nucleophilic acyl radicals at positions 4 and 5 to give 4,5-diacylpyridazines. When acyl radicals with a hydrogen atom at the a-position to the carbonyl group are used, the diacylpyridazines are mainly converted into cyclo-penta[ f]pyridazines by intramolecular aldol reactions (Scheme 43). 

Frensch and Vdgtle have recently appended three crown ether units to the cyclo-triveratrylene unit . Note that Hyatt had previously prepared the open-chained relatives of this structure (see Sect. 7.3 and Eq. 7.6). Whereas Hyatt prepared the cyclo-triveratrylene skeleton and then appended polyethyleneoxy arms to it, Frensch and Vogtle conducted the condensation reaction (formaldehyde/HCl) on the preformed benzocrown. Thus benzo-15-crown-5 was converted into the corresponding tris-crown (IS) (mp 203.5—205.5°) in 4% yield. The yield was somewhat higher for the condensation of benzo-18-crown-6, but in both cases, yield ranges were observed. These species formed 1 3 (ligand/salt) complexes with sodium and potassium ions. 

The lla-hydroxy-11,19-cyclo steroids are very efficiently converted into 19-acetoxy-11-ketones by treatment with lead tetraacetate in benzene. ... 

In contrast to the behavior of homoallylic alcohol (70a) when treated with methanesulfonyl chloride is pyridine, heating A -19-methanesulfonate (68b) in pyridine gives the 5)5,19-cyclo-6-ene (72). Vinylcyclopropane (72) is inert to the conditions used for converting vinylcyclopropane (73) to the A ° -B-homo-7)5-ol (70a). The latter results are only consistent with the existence of two discrete isomeric carbonium ion intermediates which give rise to isomeric elimination products. °... 

Still another possibility of isomerization is illustrated by the easy interconversions between pentaphenylpentadienoie aeid chloride and 2-chloropentaphenyl-3-eyelopenten-l-one. Interestingly, 2,4,6-trimethylpjrrylium iodide maj be sublimed without decomposition in a vacuum, possibly as a covalent 6-iodo-4-methyl-3,5-heptadien-2-one or 2-iodo-2,4,6-trimethyl-2H-pyran valenee isomer. In a related case, chlorocyclopropenes are covalent and are converted into cyclo-propenium derivatives only by the action of Friedel-Crafts catalysts (electron-deficient metallic chlorides) (ef. also Section II,C, 2,c.)... 

Wallach has synthesised i-menthone by condensing 1, 4-methyl-cyclo-hexanone with bromo-isobutyric ester from the condensation product he prepared i-menthene, which was converted into i-menthenone, by means of its nitrosochloride, whence i-menthone resulted by reduction. 

In the reaction of two olefins, both olefins must be adsorbed on active sites that are close together. One of these olefins becomes a paraffin and the other becomes a cyclo-olefin as hydrogen is moved from one to the other. Cyclo-olefin is now hydrogen transferred with another olefin to yield a paraffin and a cyclodi-olefin. Cyclodi-olefin will then rearrange to form an aromatic. The chain ends because aromatics are extremely stable. Hydrogen transfer of olefins converts them to paraffins and aromatics (Equation 4-11). 

Although 1-vinylnaphthalene thermally reacts with 4-acetoxy-2-cyclopenten-1-one (98) to regioselectively afford 99, the isomer 2-vinylnaphthalene gives the same thermal cycloaddition with low yield (30 %) and reacts satisfactorily only with 98 at 10 kbar (Scheme 5.10). Both products 99 and 101 were converted into the cyclopenta[a]phenanthren-15-one (100) and cyclopenta[c]phenanthren-l-one (102) isomers. Acetoxyketone 98 acts as a synthetic equivalent of cyclo-pentadienone (114 in Scheme 5.14) in cycloaddition reactions [33]. 

Giacomelli et al. constructed 3-propylisoxazole-5-yl-methanol via a [3-1-2] cycioaddition (Fig. 15) [158]. Nitrobutane was converted to nitrile oxide in the presence of 4-(4,6-dimethoxy [1,3,5]triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) and catalytic 4-dimethylaminopyridine (DMAP). Trityl chloride resin-bound propargyl alcohol was employed as the dipolarophile to trap the nitrile oxide, forming the cyclo adduct isoxazole ring under unusually mild conditions (i.e., microwave irradiation at 80 °C for five times 1 min). Disappearance of the starting material was monitored by FT-IR. 

The condensation reactions described above are unique in yet another sense. The conversion of an amine, a basic residue, to a neutral imide occurs with the simultaneous creation of a carboxylic acid nearby. In one synthetic event, an amine acts as the template and is converted into a structure that is the complement of an amine in size, shape and functionality. In this manner the triacid 15 shows high selectivity toward the parent triamine in binding experiments. Complementarity in binding is self-evident. Cyclodextrins for example, provide a hydrophobic inner surface complementary to structures such as benzenes, adamantanes and ferrocenes having appropriate shapes and sizes 12) (cf. 1). Complementary functionality has been harder to arrange in macrocycles the lone pairs of the oxygens of crown ethers and the 7t-surfaces of the cyclo-phanes are relatively inert13). Catalytically useful functionality such as carboxylic acids and their derivatives are available for the first time within these new molecular clefts. 

The intramolecular formal [3+3] cycloaddition reaction of l- [l-phenyl-2-(4-oxobut-2-enyloxy)ethyl]amino cyclo-hexen-3-one at 150°C in the presence of piperidinium acetate afforded /ra 3--l,4a-77-l-phenyl-l,2,4,4a,7,8,9,10-octahydro[l,4]oxazino[4,3- ]quinolin-7-one <2002JA10435>. At 85°C, the 6-(l-piperidnyl)-l,2,4,4a,5,6,7,8,9,10-dec-ahydro derivative formed, which could be converted into the l,2,4,4a,7,8,9,10-octahydro derivative by heating at 150 °C. Cyclization of iV-[(2-butyl-2-oxoethoxy)acetyl]-3,4-dimethoxyphenylethylamine on the action of TFA gave llb-butyl-1,3,4,6,7,1 lb-hexahydro[l,4]oxazino[3,4- ]isoquinolin-4-one <1997JOC2080>. 

A carbon-iron bond is also formed by the reaction of the cyclopropenium salt 185 with dicarbonyl(i/5-cyclopentadienyl)(trimethylsilyl)iron [92], (Scheme 69) In the reaction with benzocyclobutenylidene- 5-cyclopentadienyliron(II) hexafluorophosphate 186, CpFe(CO)2R (R=cyelo-C3H5, CH2-cyclo-C3H5) is converted to the allene and butadiene complexes, 187 and 188, respectively [93]. (Scheme 70)... 

MoC15 promotes the ring-opening transformations of cyclopropyl ketones. Cyclopropyl phenyl ketone 251 is converted to 1-phenyl-1,2,4-trichloro-1-butene 252. Desilylative lactonization of propyl 2-(trimethylsilylmethyl)cyclo-propanecarboxylate 253 yields ds-2-chloro-4-pentanolide 254 stereoselectively [144]. (Scheme 100)... 

Selenophene was also obtained as the main component in the reaction between vinylacetylene and the selenium dianion, generated from elemental selenium (Se8), in dimethyl sulfoxide-potassium-water at 100-120°C.5° Bis-y,y-dimethylallenyl selenide (18) is converted by spontaneous cyclo-aromatization to 3-isopropenyl-4-isopropylselenophene (19).51 Two mechanisms are shown in Scheme 3. 

Scheme 33 illustrates the difference in reactivity between triazolines obtained from cyclohexanone and cyclo-pentanone enamines. Thus, the reactions of azidophosphonates 239 with cyclohexanone enamines produce unstable aminotriazolines 240 that cannot be isolated due to their spontaneous elimination of amines to provide triazoles 241. Contrary to that, triazolines 242, derived from cyclopentanone enamines, are isolated in good yield (76-88%) and cannot be converted to the corresponding triazoles even by thermolysis <1995H(40)543>. Probably, introduction of a double bond between two five-membered rings would involve too much molecular strain. 

Dimethyl-4-silacyclohexadienylidene (lv) is of interest as a potential source of silaxylene 24, however, all attempts to convert the carbene into an aromatic compound failed.107 The only isolated product from gas phase reactions is the dimer 25. In solution, carbene lv was found to add stereospecifically to cis-2-butene. With butadiene as trapping reagent both the products of the 1,2- and 1,4-addition 26 and 27, respectively, are observed (Scheme 21).107 In addition, silacyclopentene 28 is formed, which is the trapping product of cyclo-... 

Hayashi et al. proposed a catalytic cycle for the rhodium-catalyzed 1,4-addition of phenylboronic acid to 2-cyclo-hexenone (Scheme 28), which was confirmed by NMR spectroscopic studies.96 The reaction presumably involved three intermediates, phenylrhodium a, oxa-7r-allylrhodium b, and hydroxorhodium c complexes. Complex a reacted with 2-cyclohexenone to give b by insertion of the carbon-carbon double bond of enone into the phenyl-rhodium bond followed by isomerization into the thermodynamically more stable complex. Complex b was converted to c upon addition of water, liberating the phenylation product. Transmetallation of the phenyl group from phenylboronic acid to rhodium took place in the presence of triphenylphosphine to regenerate a. 

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. 

Placing the electron deficient migration terminus within the original carbonyl partner converts the 1,1-cyclobutanone annulation into a 1,2- or lateral cyclo-pentenone annulation as summarized in Eq. 77. In the ring enlargement of 65 to 66,... 

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