Cyclopal

Cyclop entylidene are slightly easier to cleave than acetonides... 

Cydopentane reagents used in synthesis are usually derived from cyclopentanone (R.A. Ellison, 1973). Classically they are made by base-catalyzed intramolecular aldol or ester condensations (see also p. 55). An important example is 2-methylcydopentane-l,3-dione. It is synthesized by intramolecular acylation of diethyl propionylsucdnate dianion followed by saponification and decarboxylation. This cyclization only worked with potassium t-butoxide in boiling xylene (R. Bucourt, 1965). Faster routes to this diketone start with succinic acid or its anhydride. A Friedel-Crafts acylation with 2-acetoxy-2-butene in nitrobenzene or with pro-pionyl chloride in nitromethane leads to acylated adducts, which are deacylated in aqueous acids (V.J. Grenda, 1967 L.E. Schick, 1969). A new promising route to substituted cyclopent-2-enones makes use of intermediate 5-nitro-l,3-diones (D. Seebach, 1977). 

A similar synthesis starts from commercially available 1,5-hexadiyne and 2-methyl-cyclopent-2-enone. The benzocyclobutene is obtained from a bis-acetylene in a cobalt-catalyzed reaction. It rearranges regio- and stereoselectively to a 3-deoxy steroid derivative. The overall yield from the cyclopentenone was 40% (R.L. Funk, 1977). 

Corray 40 carbon black cyclop araffinic hydrocarbon processing aid softens, swells, and smooths reclaim reinforcing filler... 

In order to obtain pure aromatics, cmde reformate is extracted to separate the aromatics from unreacted paraffins and cyclop araftins. The aromatics are, in turn, separated by simple fractional distillation to yield high purity benzene, toluene, xylenes, and aromatics. 

D. Navinchandra, "Case-Based Reasoning in CYCLOPS, A Design Problem Solver," in Ref. 82. 

Azabicyclop.2.0]heptane circular dichroism, 7, 356 nomenclature, 7, 342 7-Azabi cyclop. 1.0]heptane synthesis, 7, 85-86 3-Azabicyclo[4.1.0]heptene, 7, 544 2-Azabicyclop.2.0]hept-6-en-3-one synthesis... 

Azabicyclo[2.2.0]hexa-1,3,5-triene reactions, 7, 360 2-Azabicyclo[2.2.0]hex-5-ene reactivity, 7, 342 synthesis, 2, 371 2-Azabi cyclop. 1.0]hexene synthesis, 2, 371 2-Azabi cyclop. 1.0]hex-2-ene synthesis, 7, 67 2-Azabicyclo[k 1.0]hex-3-ene synthesis, 4, 258 6-Azabicyclo[k 1.0]hex-2-ene synthesis, 2, 305 Azabi cyclohexenes formation from azirines, 7, 58... 

Cyclopent-2-en-l-one, 2-hydroxy-3-methyl-synthesis, 3, 693 Cyclopentenone, 4-methoxy-formation, 1, 423 Cyclopenthiazide as diuretic, 1, 174 Cyclopent[2,3-d]isoxazol-4-one structure, 6, 975 Cyclophane conformation, 2, 115 photoelectron spectroscopy, 2, 140 [2,2]Cyclophane conformation, 2, 115 Cyclophanes nomenclature, 1, 27 Cyclophosphamide as pharmaceutical, 1, 157 reviews, 1, 496 Cyclopiloselloidin synthesis, 3, 743 Cyclopolymerization heterocycle-forming, 1, 292-293 6H-Cyclopropa[5a,6a]pyrazolo[l,5-a]pyrimidine pyrazoles from, 5, 285 Cydopropabenzopyran synthesis, 3, 700 Cyclopropachromenes synthesis, 3, 671 Cyclopropa[c]dnnolines synthesis, 7, 597 Cyclopropanation by carbenes... 

SOURCE Courtesy of Bridgeville Stainless Division, Cyclops Industries, Inc. 

The selective protection of the 17-ketone is difficult to achieve in the presence of other carbonyl groups on account of the reduced reactivity of cyclopent-anones as compared to cyclohexanones. On the other hand, cleavage of a... 

S-Benzyl Thiocarbamate, 548 Butynyl, 548 p-Cyanobenzyl, 548 Cyclobutyl, 548 Cyclohexyl, 548 Cyclopentyl, 548 Cyclop ropy I methyl, 548 p-Decyloxybenzyl, 548 Diisopropylmethyl, 548 2,2-Dimethoxycarbonylvinyl, 548... 

The malonic ester required for synthesis of cyclopal (107) can be obtained by alkylation of diethyl allylmalonate (115) with 1,2-dibromocyclopentane in the presence of excess base. It is probable that the reaction proceeds by elimination of hydrogen bromide from the dihalide as the first step. The resulting allilic halide (116) would be the most reactive electrophile in the reaction mixture and thus would quickly alkylate the anion of the malonate to afford 117. 

Miller and coworker report a total syndiesis of carbocyclic polyoxin C from cis-(N- en-butylcarbamoyl cyclopent-2-en-Tol, as shovm in Scheme 5.11. This syndiesis feanires a... 

A novel splropentanopyrrolmdine oxime has been isolated from skin extracts of the Panamanian poison frog. This alkaloid can besynthesized via the Michael addi don of cyclop en-tanecarboxaldehyde to nitroethene fScheme 10.19. ... 

Q -Hydroxy-3Q (tetrahydropyran-2-yloxy)-2/3-(3Q -tetrahydropyran-2-yloxy-4-phenoxy-trans-1-buten-1 -yl)cyclopent-1Q -yl] -acetaldehyde a-hemiacetal Chromic anhydride Methanesulfonyl isocyanate Acetic acid... 

The cyclopentazepine systems are often1-5 referred to as 4-aza-, 5-aza-, and 6-azaazulene, respectively. Confusingly, the cyclopent[a]azepine 8a, which is more correctly known as 1ff-pyrrolo[l,2-a]azepine, has been referred to as 4-azaazulene6 and as 3a-azaazulene.7 Only the carbonyl derivative 8b of this nonconjugated system is included in this section since it can be represented as the fully conjugated, aromatic, dipolar structure 9.6... 

The parent cyclopent[Z>]-2 and cyclopent[c]azepine4 ring systems are known and have been fully characterized. Cyclopent[t/]azepine has also been reported54 but no full experimental details or properties of this system have been published. 

Unlike the isomeric cycloheptapyrroles, in which the nitrogen is located in the five-mem-bered ring, the cyclopentazepines are unstable for example, cyclopent[/)]azepine is stable in solution in the dark, but slowly decomposes in light and rapidly in the presence of oxygen.2 The deep turquoise crystals can, however, be stored in a refrigerator. The sapphire blue 1-bromo-2-ethoxycyclopent[ /]azepine is also photosensitive.55... 

The H and 13CNMR spectra of various cyclopentazepines have been recorded (Tables 1 and 2), as has the HNMR spectrum of 7V,7V-dimethylcyclopent[e]azepin-l-amine.68 A detailed analysis of geminal and long-range 13C-H coupling constants for cyclopent[c]azepine is also available.87 The HNMR spectra of 9//-pyrrolo[l,2-a]azepin-9-one (8b) and its fully delocalized cation have been recorded in various solvents.7... 

The triplet nitrenium ion, however, lacks symmetry but, unlike the excited triplet states of other azaaromatic systems such as pyridine, is surprisingly planar.283 Theoretical dipole moments for cyclopent[c]- and cyclopent[rf]azepine, and the molecular geometry of cyclopent[rf]-azepine, have been calculated using semiempirical ab initio methods.3... 

The first cyclopent[A]azepine 19 was obtained as dark-green crystals by the acid-catalyzed condensation of 4-hydroxy-2,3,4-triphenylcyclopent-2-en-l-one (18) with pyrrolidine in refluxing toluene.106... 

The addition of dimethyl acetylenedicarboxylate to 5-/er/-butyl-Ar,Ar,Ar, Ar -tetramethyl-2-aza-pentalene-1,3-diamine (20) is frontier orbital rather than charge controlled, and results initially in attack at the 3a-position to give, via a dipolar intermediate, tricycle 21, which undergoes valence isomerization to the cyclopent[c]azepine 22.107... 

The process of dehydrohalogenation has been used on several occasions to prepare cyclopent-azepine and indenoazepine ring systems. 

An elegant extension of these intramolecular acylnitrene-induced ring expansions has been used for the synthesis of cyclopent[h]azepines.2 2-Haloindan-l-yl azidoformates 14 (X = Cl, Br), when subjected to pyrolysis at 300 °C in a hot tube packed with calcium oxide and copper turnings, produce cyclopent[6]azepine (15), as a dark turquoise oil, in excellent yield. Lesser yields (30 and 50%, respectively) of the 4-bromo and 3-methoxy derivatives can be similarly obtained. 

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