Sulfones, cyclopentyl

In further modifications of these norprogestins, reaction of norethindrone with acetic anhydride in the presence of p-toluene-sulfonic acid, followed by hydrolysis of the first-formed enol acetate, affords norethindrone acetate (41). This in turn affords, on reaction with excess cyclopentanol in the presence of phosphorus pentoxide, the 3-cyclopentyl enol ether (42) the progestational component of Riglovic . Reduction of norethindrone affords the 3,17-diol. The 33-hydroxy compound is the desired product since reactions at 3 do not show nearly the stereoselectivity of those at 17 by virtue of the relative lack of stereo-directing proximate substituents, the formation of the desired isomer is engendered by use of a bulky reducing agent, lithium aluminum-tri-t-butoxide. Acetylation of the 33,173-diol iffords ethynodiol diacetate, one of the most potent oral proves tins (44). ... 

Benzenesulfnmc acid, 4-methyl-, cyclopentyl ester [Cyclopentanol, p-toluene-sulfonate], 55, 112... 

A wealth of chemistry has emerged from the solvolysis studies of cyclobutylmethyl sulfonates and related compounds, which are able to undergo ring enlargement to cyclopentyl systems via the cations. A schematic representation of this reaction is shown. Some ring-expansion reactions to be classified under this category are also shown and further examples are discussed.27 24... 

In case (a), labelled secondary alkyl benzenesulfonates (alkyl = 2-adamantyl, 2-propyl, cyclopentyl, etc.) with 18-28% of lsO in the sulfonyl group were partially solvolysed in a range of solvents (SOH), and recovered unreacted alkyl benzenesulfonates were then subject to reductive cleavage of the O—S bond of the sulfonate ester [39]. For water as solvent, the... 

Methanesultonyl chloride Cyclopentyl methanesul Innate (a sulfonyl chloride) (a sulfonate ester)... 

Sulfon (l-Nitro-cyclopentyl)-phenyl-E19a, 409 (H S02-R) 5-Thia-l-aza-bicyclo[4.2.0]oct-2-en ... 

Brown s approach was to show that the properties ascribed to the nonclassical ion could be duplicated in systems involving classical carbocations. Since the rate enhancement of solvolysis of the exo isomer was an important part of the argument for (7-bond participation, he also analyzed the relative reactivities of various systems. He argued that the cxo-norbomyl system should be compared to the cyclopentyl system rather than to cyclohexyl brosylate. The torsional relationship of the leaving group and adjacent substituents is eclipsed in norbomyl sulfonates, and strain is relieved on ionization. Cyclohexyl brosylate, in contrast, is completely staggered in the ground state, and so no strain relief accompanies ionization. In the cyclopentyl... 

The antifungal, antiviral agent (+)-brefeldin A, whose recent synthesis using rr-allyl-paUadium complexes has previously been described (Scheme 24), was prepared by Trost et using the [3 + 2] cycloaddition to form the cyclopentyl ring (Scheme 41). Chiral acrylate 190, prepared from mannitol, was subjected to cyclizalion conditions to give cycloadduct 191 in 87% yield and an excellent selectivity. Diastereoselectivity in the cycloaddition extended the stereochemistry of 190 into the absolute stereochemistry of 191, generating three of the live stereocenters of brefeldin A. After ozonolysis, reduction, and protection, the lower side chain was attached to prepare the sulfone 192. The upper side chain was then introduced, and further functionalization led to the key intermediate 194, which had already been transformed to (+)-brefeldin A. 

Cyclization of a-sulfonyl-or a-cyano-e-acetylenic esters to al-lylic cyclopentyl sulfones or nitriles is promoted by copper iodide. The reaction has been shown to go through a vinylic copper species. A catalytic version has heen developed using r-BuOK (15 mol %) as ahase and Cul (10 mol %) in THF (eq 19). Other cyclizations reported include the copper iodide-catalyzed cyclization of IV-aUylhalodtfluoroacetamides, which allows the synthesis of a,a-dtfluorinated-)/-lactams, and the copper iodide-assisted synthesis of new Se—N heterocycles. ... 

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