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Seven-membered

When they treated TM 381 with base (MeO in MeOH) it was in fact 381A which was formed, so five membered rings are better than seven membered rings (J. Org. Chem.. 1976, 41, 2955). [Pg.122]

The synthesis of five-, six-, and seven-membered cyclic esters or timides uses intramolecular condensations under the same reaction condifions as described for intermolecular reactions. Yields are generally excellent. An example from the colchicine synthesis of E.E. van Ta-melen (1961) is given below. The synthesis of macrocyclic lactones (macrolides) and lactams (n > 8), however, which are of considerable biochemical and pharmacological interest, poses additional problems because of competing intermolecular polymerization reactions (see p. 246ff.). Inconveniently high dilution, which would be necessary to circumvent this side-... [Pg.145]

Since 1,2- to 1,6-difunctional opengeneral procedures (see chapter 1), it is useful to consider them as possible starting materials for syntheses of three- to seven-membered heterocycies 1,2-heterocycles can be made from 1,2-difunctional compounds, e.g. olefins or dibromides 1,3-difunctional compounds, e.g. 1,3-dibromides or 1,3-dioxo compounds, can be converted into 1,3-heterocycles etc. [Pg.148]

The 1,6-difunctional hydroxyketone given below contains an octyl chain at the keto group and two chiral centers at C-2 and C-3 (G. Magnusson, 1977). In the first step of the antithesis of this molecule it is best to disconnect the octyl chain and to transform the chiral residue into a cyclic synthon simultaneously. Since we know that ketones can be produced from add derivatives by alkylation (see p. 45ff,), an obvious precursor would be a seven-membered lactone ring, which is opened in synthesis by octyl anion at low temperature. The lactone in turn can be transformed into cis-2,3-dimethyicyclohexanone, which is available by FGI from (2,3-cis)-2,3-dimethylcyclohexanol. The latter can be separated from the commercial ds-trans mixture, e.g. by distillation or chromatography. [Pg.206]

Carbonylation of halides in the presence of primary and secondary amines at I atm affords amides[351j. The intramolecular carbonylation of an aryl bromide which has amino group affords a lactam and has been used for the synthesis of the isoquinoline alkaloid 498(352], The naturally occurring seven-membered lactam 499 (tomaymycin, neothramycin) is prepared by this method(353]. The a-methylene-d-lactam 500 is formed by the intramolecular carbonylation of 2-bromo-3-alkylamino-l-propene(354]. [Pg.196]

Dimethyl iodo(4-pentenyl)malonate (926) undergoes a Pd-catalyzed intramolecular radical-type reaction to form the alkyl iodides 927 and 928. rather than a Heck-type reaction product(775]. The same products are also obtained by a radical reaction promoted by tin hydride(776]. Although yield was low, a similar cyclization of the n-chloro ester 929 to form the seven-membered ring 930 was ob,served(777(. [Pg.263]

The ligand effect seems to depend on the substrates. Treatment of the prostaglandin precursor 73 with Pd(Ph3P)4 produces only the 0-allylated product 74. The use of dppe effects a [1,3] rearrangement to produce the cyclopen ta-none 75(55]. Usually a five-membered ring, rather than seven-membered, is predominantly formed. The exceptionally exclusive formation of seven-membered ring compound 77 from 76 is explained by the inductive effect of an oxygen adjacent to the allyl system in the intermediate complex[56]. [Pg.302]

A radically different course is followed when the reaction of 2-alkyl-substituted thiazoles is periormed in methanol or acetonitrile (335), 2 1 adducts containing seven-membered azepine rings (91) are being formed in which two of the original activated hydrogen atoms have altered positions (Scheme 55). A similar azepine adduct (92) was obtained by... [Pg.98]

Dieckmann cyclization (Section 21 2) An intra molecular analog of the Claisen condensation Cy die p keto esters in which the ring is five to seven membered may be formed by using this reaction... [Pg.906]

The chiral recognition mechanism for these types of phases was attributed primarily to hydrogen bonding and dipole—dipole interactions between the analyte and the chiral selector in the stationary phase. It was postulated that chiral recognition involved the formation of transient five- and seven-membered association complexes between the analyte and the chiral selector (117). [Pg.70]

Caprolactam [105-60-2] (2-oxohexamethyleiiiiriiQe, liexaliydro-2J -a2epin-2-one) is one of the most widely used chemical intermediates. However, almost all of the aimual production of 3.0 x 10 t is consumed as the monomer for nylon-6 fibers and plastics (see Fibers survey Polyamides, plastics). Cyclohexanone, which is the most common organic precursor of caprolactam, is made from benzene by either phenol hydrogenation or cyclohexane oxidation (see Cyclohexanoland cyclohexanone). Reaction with ammonia-derived hydroxjlamine forms cyclohexanone oxime, which undergoes molecular rearrangement to the seven-membered ring S-caprolactam. [Pg.426]

The possible variations among the three atoms comprising this reactive component make this the largest group and the one with the most potential for further development. They are particularly useful in the synthesis of five-, six- and seven-membered ring systems. They also may be conveniently considered according to their atom composition, and the hybridization state of any carbon atoms involved. [Pg.124]

Dipolarophiles utilized in these cycloadditions leading to five-membered heterocycles contain either double or triple bonds between two carbon atoms, a carbon atom and a heteroatom, or two heteroatoms. These are shown in Scheme 9 listed in approximate order of decreasing activity from left to right. Small rings containing a double bond (either C=C or C=N) are also effective dipolarophiles, but these result in six- and seven-membered ring systems. [Pg.143]

Fully saturated seven-membered heterocycles with one or two heteroatoms are normally in mobile twist-chair conformations (Section 5.17.1.1, Chapter 5.18) (b-77SH(2)123). Annelation and the introduction of exocyclic double bonds can have profound effects oxepan-2-one, for example, is in a near chair conformation (67JA5646). [Pg.14]

Table 10 Structure and H NMR Data of Seven-membered Heterocyclic Compounds... Table 10 Structure and H NMR Data of Seven-membered Heterocyclic Compounds...
The NMR spectra of heterocyclic compounds with seven or more ring members are as diverse as the shape, size and degree of unsaturation of the compounds. NMR is perhaps the most important physical method to ascertain the structure, especially the conformational statics and dynamics, of large heterocycles. Proton-proton coupling constants provide a wealth of data on the shape of the molecules, while chemical shift data, heteroatom-proton coupling constants and heteronuclear spectra give information of the electronic structure. Details are found in Chapters 5.16-5.22. Some data on seven-membered rings are included in Table 10. [Pg.16]

Preparation of spirooxaziridines from cyclic ketones poses no problems nor does oxaziridine synthesis from cyclic Schiff bases, which was preferably carried out with pyrro-lines to give, for example (245) (59JCS2102) and, in connection with tranquilizer synthesis, with heterocyclic seven-membered rings to give, for example, (246) (63JOC2459). [Pg.228]

The TIPDS derivative can be induced to isomerize from the thermodynamically less stable eight-membered ring to the more stable seven-membered ring derivative. The isomerization occurs only in DMF. [Pg.139]

Substituent effects (electronegativity, configuration) influence these coupling constants in four-, five- and seven-membered ring systems, sometimes reversing the cis-tmns relationship so that other NMR methods of structure elucidation, e.g. NOE difference spectra (see Section 2.3.5), are needed to provide conclusive results. However, the coupling constants of vicinal protons in cyclohexane and its heterocyclic analogues (pyranoses, piperidines) and also in alkenes (Table 2.10) are particularly informative. [Pg.44]

These steric factors are also indicated by the relative basicity of enamines derived from five-, six-, and seven-membered ketones. The five- and seven-membered enamines are considerably stronger bases, indicating better conjugation between the amine lone pair and the double bond. The reduced basicity of the cyclohexanone enamines is related to the preference for exo and endo double bonds in six-membered rings (see Section 3.10). [Pg.432]

The Hiickel rule predicts aromaticity for the six-7c-electron cation derived from cycloheptatriene by hydride abstraction and antiaromaticity for the planar eight-rc-electron anion that would be formed by deprotonation. The cation is indeed very stable, with a P Cr+ of -1-4.7. ° Salts containing the cation can be isolated as a product of a variety of preparative procedures. On the other hand, the pK of cycloheptatriene has been estimated at 36. ° This value is similar to those of normal 1,4-dienes and does not indicate strong destabilization. Thus, the seven-membered eight-rc-electron anion is probably nonplanar. This would be similar to the situation in the nonplanar eight-rc-electron hydrocarbon, cyclooctatetraene. [Pg.526]

Derive the tc-MO patterns for these three molecules by treating them as derivatives of the three-, five-, and seven-membered cyclic conjugated systems. Explain the relationship between the derived MO pattern and the observed properties and stabilities of the molecules. [Pg.548]


See other pages where Seven-membered is mentioned: [Pg.113]    [Pg.133]    [Pg.84]    [Pg.151]    [Pg.301]    [Pg.326]    [Pg.480]    [Pg.545]    [Pg.147]    [Pg.207]    [Pg.107]    [Pg.342]    [Pg.386]    [Pg.267]    [Pg.132]    [Pg.172]    [Pg.14]    [Pg.14]    [Pg.22]    [Pg.23]    [Pg.33]    [Pg.57]    [Pg.65]    [Pg.2]    [Pg.96]    [Pg.101]    [Pg.166]    [Pg.494]    [Pg.602]   


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1,4-Conjugate addition seven-membered rings

Approaches to Seven-Membered Rings

Beckmann rearrangements seven-membered rings

Carbon seven-membered ring formation

Conformations of the Seven-Membered Rings

Cope rearrangements seven-membered ring synthesis

Cyclic Allenes Up to Seven-Membered Rings

Cyclic compounds seven-membered rings

Cyclic ether seven-membered

Cyclic ketal, seven-membered

Cycloadditions seven-membered ring synthesis

Five- and Seven-membered Ring Systems

Formation of Seven-Membered Cycles

Formation of Seven-membered Carbocycles by RCM

Formation of seven-membered ring

Halogenation six- and seven-membered rings

Heck reaction seven-membered rings

Heteroatom heterocycles Seven-membered

Heterocyclic compounds seven-membered ring opening

Heterocyclic compounds seven-membered rings

Heterocyclic synthesis seven-membered rings

Imine compounds seven-membered rings

Imines seven-membered cyclic

Ketones seven-membered ring synthesis

Lactams seven-membered

Lactams seven-membered, hydrolysis

Lactones seven-membered

Lactones seven-membered ring

Medium Size (Seven- to Nine-Membered Rings)

Metallacycles seven-member

N-Heterocyclic Carbenes Derived from Six- or Seven-membered Heterocycles

Nickelacycle, seven-membered

Nitrile imines seven-membered rings

Nitrogen-containing heterocycle synthesis seven-membered ring heterocycles

Nitrogen-ring systems, seven-membered

Nitronates Preparations cyclic-seven-membered

Other Cycloadditions Leading to Seven-Membered Rings

Other Seven-Membered Heterocycles Fused to a Benzene Ring

Other six-and seven-membered rings

Pharmacologically active seven-membered

Phosphorus seven-membered rings

Polycyclic Arenes Containing Seven-Membered Carbocydes

Racemic seven-membered lactones

Ring closures seven-membered

Ring compounds, structure seven-membered

Ring structure seven-membered rings

Rings seven-membered, conformations

Rings, seven-membered, from acyclic

Rings, seven-membered, from acyclic precursors

SEVEN-MEMBERED HETEROCYCLIC RINGS FUSED TO BENZENE

Seven membered cyclic ethers cyclization

Seven membered ring formation

Seven- and Eight-membered Rings

Seven-, Eight- and Nine-membered Rings

Seven-Membered Heterocycled

Seven-Membered Heterocydes

Seven-Membered Rings from Fragmentation Strategies

Seven-Membered Tellurium Heteroarenes

Seven-Membered and Larger Ring Systems

Seven-and Eight-Membered Carbocycles

Seven-membered NHC

Seven-membered Rings containing Three or More Heteroatoms

Seven-membered and larger heterocycles

Seven-membered carbocycles

Seven-membered carbocycles synthesis

Seven-membered carbohydrate ring

Seven-membered cyclic compounds

Seven-membered cyclic compounds preparation

Seven-membered cyclic-a-adduct

Seven-membered cycloadditions

Seven-membered heteroaromatic ring

Seven-membered heterocycle-containing

Seven-membered heterocycle-derived

Seven-membered heterocycle-derived carbenes

Seven-membered heterocycles

Seven-membered heterocycles literature reviews

Seven-membered heterocycles with three heteroatom

Seven-membered heterocycles, review

Seven-membered intramolecular

Seven-membered intramolecular hydrogen bonds

Seven-membered ketone

Seven-membered lactam

Seven-membered nitrogen heterocycle

Seven-membered oxepane

Seven-membered oxepanes

Seven-membered ring

Seven-membered ring compounds, synthesis

Seven-membered ring generation

Seven-membered ring heterocycles

Seven-membered ring heterocycles reviews

Seven-membered ring heterocycles with

Seven-membered ring heterocydes

Seven-membered ring product

Seven-membered ring systems

Seven-membered rings Friedel-Crafts reaction

Seven-membered rings Prins reaction

Seven-membered rings Seychellene

Seven-membered rings aldol reaction cascade

Seven-membered rings five-atom tether

Seven-membered rings intramolecular aldolization of keto aldehydes

Seven-membered rings synthesis

Seven-membered rings three heteroatoms

Seven-membered rings via -cycloadditions

Seven-membered rings, heterocyclic

Seven-membered rings, ring-closing metathesis

Seven-membered rings, ring-closing metathesis strategy

Seven-membered rings, synthesis cycloaddition strategies

Seven-membered systems containing three or more heteroatoms

Seven-membered systems containing two heteroatoms

Seven-membered systems of pharmacological significance

Seven-membered trans-cycloalkene

Seven-membered, Medium, and Large Rings

Six- and Seven-membered Rings

Six-, seven-, nine- and ten-membered rings

Strategies for Seven-Membered Ring Synthesis

Sulfone, seven-membered

Synthesis of Seven- and Eight-Membered Rings

Synthesis of Seven-Membered Rings

Synthesis of seven-membered carbocycle

Ylide compounds seven-membered rings

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