Seven-membered ring product

The intramolecular variant of the Friedel-Crafts alkylation is also synthetically useful, especially for the closure of six-membered rings, e.g. the synthesis of tetraline 8 but five- and seven-membered ring products are also accessible ... 

Using the same rhodium catalyst, Brummond has also observed the formation of seven-membered ring products and applied to interesting syntheses of azepines and oxepines (Scheme 123). 

When internal alkynes are used, no silane is necessary for the reaction, although slightly elevated temperatures are required (Scheme 75).3 Interestingly, it was determined that terminal alkynes yield more of the [2 + 2 + 21-cycloadducts when no silanes are used in the reaction while internal alkynes only produce the [2 + 2 + 2]-products when silanes are present (Equation (47)). Two distinct mechanisms for the [2 + 2 + 2 + l]-reactions, both leading to the seven-membered ring products, have been proposed (Schemes 76 and 77). 

The oxidation of enol ethers at a reticulated vitreous carbon anode [2, 3] (Scheme 1) in a mixture of methanol/THF containing tetraethylammonium tosylate as the electrolyte and 2,6-lutidine as the base leads to substituted tetrahydrofu-ran and tetrahydropyran rings in good yields (51-96%). The major product obtained had a trans-stereochemistry. The cyclization failed to make seven-membered ring products. In order to determine the... 

Intramolecular cyclization can also be initiated from the radical-cation of a styrene residue [57], Oxidative cyclization of 31, n = 1 and 31, n = 2 give five and seven membered ring products respectively but in contrast 32 failed to yield a five membered ring product, giving only intractable mixtures. This difference in reactivities can be explained in terms of Baldwin s rules where the 5-endo-trig cyclization of the radical-cation from 32 is disfavoured [58]. 

Intramolecular coupling of substrates having both carbonyl and diphenyldiazenyl groups proceeds with Sml2 and HMPA in THF to give five- to seven-membered ring products (Equation (71)). Selectivity of the cyclization is... 

A net C—O to C—C bond chirality transfer has been demonstrated in the preparation of a cyclopropane (equation 344).428 Another C—O to C—C chirality transfer was accomplished starting with an optically active alkylidenetetrahydrofuran 429 Not only was complete stereospecificity via a double inversion mechanism observed, but, in addition, regioselectivity had to be exercised to avoid the alternate cycliza-tion to give a seven-membered ring product (equation 345). 

Treatment of 106 with silylated enediols 105 in the presence of TMSOTf gives the corresponding annulated bicyclic diols 107 (equation 82)151. A similar reaction with cyclobutenediol derivative 108 followed by oxidative cleavage of thus formed diol 109 yields a seven-membered ring product (equation 83). 

Both methods provide four-, five-, six-, and seven-membered-ring products, affording a single regioisomer of the zirconacycle 25. The substrate can possess... 

Allyl alcohol with three terminal methyl groups, such as (4c X = OH, Y = Me), reacts with cyclopen-tadiene under two-phase conditions (in an aqueous p-toluenesulfonic acid/pentane solution) to give a seven-membered ring product (26) (Scheme 8). ... 

Hoffman et al. have reported that reaction of the 2-methylallyl cation with cyclopentadiene affords seven-membered ring products. ... 

The seven-membered ring product (49 equation 17) is obtained as a mixture of the trans and cis isomers (82 18) in 67% yield from the reaction of (26) with dimethyl muconate (48) in the presence of a... 

Lewis acid-catalyzed reaction with dichloroketene results in net insertion of the ketene into the ring to form the seven-membered ring products 110 (Equation 15) <1996AGE1970>. 

In some cases, abstraction-recombination can lead to still larger rings. In the example illustrated, 1,8-hydrogen atom extraction leads to the formation of a seven-membered ring product (119 equation 42). The 1,7-diradical would be thermodynamically favored because of the radical-stabilizing ability of the two sulfur atoms. The reaction may not, however, proceed by direct 1,8-abstraction. A 1, S-abstraction followed by a subsequent 1,4-abstraction would give the same product and would be sterically more reasonable. 

A single example is known for a palladium(0)-catalyzed cotrimerization reaction involving two molecules of an alkene and a methylenecyclopropane molecule, leading to the formation of a seven-membered-ring product.The reaction is limited to unsubstituted allene and, along with the cyclotrimer, l,3,5-tris(methylene)cycloheptane (3), 1,3-bis(methylene)cyclopen-tane (2), the product of a [3 + 2] cycloaddition, is also obtained. The product ratio 2/3 is markedly dependent on the catalyst composition. Additionally, the allene trimer, 1,2,4-tris(methyl-ene)cyclohexane (4), and the methylenecyclopropane homodimer, 5-methylenespiro[2.4]hep-tane (5), are formed. 

As noted in Section 2.2.2.3.2.1.1.1. seven-membered-ring products are obtained, as mixtures of CIS- and tranj-isomers, from the palladium(0)-catalyzed reaction of dimethyl ( , )-hexa-2,4-dienedioate (2) with MCP (i).i2a,66c, 119 nickel(0)/phosphite catalyst systems are employed, the selectivity for the formation of the [3 -I- 2] cycloadduct 3 increases. More interestingly, only cis-4 is formed in these cases. 

The synthesis of l,3-oxazepin-2-one derivatives (64) by the reaction of vinyloxiranes (63) with chlorosulfonylisocyanate has been described (Equation (5)) <92CL1575>. Yields of the seven-membered ring products were generally excellent (Table 2). 

Cyclodihydrocodeinone, on catalytic reduction, yields 14-methyl-C-nordihydrocodeinone (144), which, on ring expansion with diazomethane, yields 14-methyldihydrocodeinone and the related 6-spiro-oxiran, together with the corresponding seven-membered ring products of further expansion. ... 

A recent report from Snider shows another variant of a radical-mediated, ring-forming reaction (Eq. 10). This process technically produces both a six- and seven-membered ring product. 

Although simple vinylcyclopropanes have not proven useful, Fowler reported in 1971 that a homopyrrole, a constrained and heteroatom-activated vinylcyclopropane, reacts with alkynes to produce a seven-membered ring product (Eq. 44). A zwitterionic intermedi-... 

Herges and Ugi reported an analogous reaction between homofuran and tetracyanoethylene which leads to a seven-membered ring product (Eq. 45). These authors, however, favor a concerted pathway for this... 

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