Chlorosulfonyl isocyanate reaction with alkenes

W-C4H9) [106, 107]. Ab initio MO calculations have shown that the [2 - - 2] cycloaddition between cis- or Jraw-alkenes and isocyanates to yield y9-lactams takes place by a concerted mechanism in the gas phase, with retention of the alkene configuration in the product. However, increasing solvent polarity contributes to the asynchronicity of the reaction to such an extent that the mechanism changes from a concerted to a two-step process involving a zwitterionic intermediate, with a consequent loss of alkene stereospecificity, as observed in the reaction between chlorosulfonyl isocyanates and vinyl ethers [794]. 

Menthol [(—)-l] has been used as a chiral ligand for aluminum in Lewis acid catalyzed Diels-Alder reactions with surprising success2 (Section D.l.6.1.1.1.2.2.1). The major part of its application is as a chiral auxiliary, by the formation of esters or ethers. Esters with carboxylic acids may be formed by any convenient esterification technique. Esters with saturated carboxylic acids have been used for the formation of enolates by deprotonation and subsequent addition or alkylation reactions (Sections D.l.1.1.3.1. and D.l.5.2.3.), and with unsaturated acids as chiral dienes or dienophiles in Diels-Alder reactions (Section D. 1.6.1.1.1.), as chiral dipolarophiles in 1,3-dipolar cycloadditions (Section D.l.6.1.2.1.), as chiral partners in /(-lactam formation by [2 + 2] cycloaddition with chlorosulfonyl isocyanate (SectionD.l.6.1.3.), as sources for chiral alkenes in cyclopropanations (Section D.l.6.1.5.). and in the synthesis of chiral allenes (Section B.I.). Several esters have also been prepared by indirect techniques, e.g.,... 

An alternative approach to the p-lactam ring system uses the cycloaddition of an alkene with an isocyanate such as chlorosulfonyl isocyanate (0=C= N—SOiCl). For example, reaction of cyclopentadiene with chlorosulfonyl isocyanate gave the p-lactam 183 (3.121). The A-unsubstituted -lactam is formed under these conditions owing to the ease of removal of the SO2CI group. The regioselectivity can be explained by combination of the more electron-rich end of the alkene with the electron-dehcient carbon atom of the isocyanate. 

Woodward s synthesis, 4, 416-419 Chlorophyll b, 4, 382 Chlorophyll c, 4, 382 Chlorophyll d, 4, 382 Chlorophylls, 4, 378 biosynthesis reviews, 1, 99 structure, 4, 370 substituents reactions, 4, 402 Chloroporphyrin e6, 4, 404 Chloroprothixene pharmacology, 3, 942 Chloropyramine as antihistamine, 1, 177 Chloropyrifos synthesis, 2, 201 Chloropyrifos-ethyl as insecticide, 2, 516 Chloropyrifos-methyl as insecticide, 2, 516 Chloroquine, 1, 145 adsorption on nucleic acids, 1, 179 as antimalarial, 1, 173, 2, 517 Chloroquine, hydroxy-as antimalarial, 2, 517 Chlorosulfonyl isocyanate cycloaddition reactions with alkenes, azetidin-2-ones from, 7, 261 reactions... 

Chlorosulfonyl isocyanate reacts with a wide range of alkenes under mild conditions to produce 3-lactams (25) accompaniedby variable but usually minor amounts of open-chain adducts (26 Scheme 27). In most cases, 3-lactams and open-chain products are formed independently. Thus N-chlorosulfonyl amide by-products are not formed by further reaction of N-chlorosulfonyl-3-lactams. 

An alternative route to chiral p-lactams was provided by reactions of electron-deficient isocyanates with chiral nucleophilic alkenes such as vinyl ethers or vinyl acetates. Chlorosulfonyl isocyanate (CSI), a commonly used reactive isocyanate [34], undergoes stereospecific 5-yn-addition to alkenes. The chlorosulfonyl group can subsequently be reductively removed from the nitrogen atom. It has been shown that reactions between CSI and (Z)- and ( )-alkenyl ethers stereoselectively give cA-3,4-disubstituted azetidinones from (Z)-olefins and tmns-3,4-... 

The reaction of A-chlorosulfonyl isocyanate with alkenes has been used as a method of constructing nine-membered lactams. Thus, the spirocyclopropane (285) reacted exclusively at the methylene rather than at the isoprenyl alkene to generate a zwitterionic intermediate (286), which cyclized to give the nine-membered lactam (287) as the major product (Scheme 34) <78TL2613>. 

Reactions 1-4 use N-chlorosulfonyl isocyanate (2.8S CSI) in reactions with various alkene moieties. When CSI reacted with 3-chloro-2-methylpropene in reaction 1, p-lactam 2.93 was produced.49 Deprotection of the nitrogen was followed by hydrolysis to give 3-amino-4-chloro-3-methylbutanoic acid (2.94). 

Silver acetate catalyses the cycloaddition of methyl isocyanoacetate with electron-deficient alkenes to produce A - or A -pyrrolines in good yields. The reaction of 3-acetoxy-l-methylallylsilane with A-chlorosulfonyl isocyanate at 0°C produces the... 

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