Isocyanates, reaction with cyclopropanes

While simple unactivated cyclopropanes have yet to be used for [3 + 2] cycloaddition, Tsuji and coworkers have developed a palladium-catalyzed cycloaddition reaction using electron-deficient vinylcy-clopropanes. Thus, vinylcyclopropane (43) undergoes smooth cyclization with methyl acrylate in the presence of a palladium catalyst to give vinylcyclopentane (44) as a mixture of diasteroisomers (equation 35). The cycloaddition probably proceeds through the zwitterionic ( ir-allyl)palladium intermediate (45) and its stepwise reaction with the acrylate (equation 36). Enones such as cyclopentenone and methyl vinyl ketone will also react. Reaction of the same vinylcyclopropane with phenyl isocyanate produces vi-nyllactam (46) (equation 37).Some cycloaddition reactions with (cyclopropyl)Fp complexes have also been reported. However, the substrates are limited to SO2 and TCNE and the yields have not been disclosed (equation 38). ... 

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.,... 

The cyclopropane rings of ds-bicyclo[6,l,0]nona-2,4,6-trienes are opened in reactions with chlorosulphonyl isocyanate, though this electrophile bonds initially to C-3 of the trienyl group then ring-closes on to C-4 to give a trans-ring junction trans-1,3-bishomotropylium ions have been proposed as intermediates (see also p. 120). The spiro[2,6]nonatrienylmethyl derivative... 

The vinylcyclopropanes (1) and (5) react with chlorosulfonyl isocyanate (CSI) (1, 117-118 2, 70 3, 51-53 this volume) in different ways. Thus (1) reacts with CSI (CH2C12, 0") to give (9). In the case of (1) the cyclopropane ring is retained in the reaction of (5) the cyclopropane ring is opened. A possible explanation for the contrasting behavior of (1) and (5) has been suggested. 

Thus, reaction of the dicarbonate with malonate produces vinylcyclopropanes as reported by Tsuji and co-workers in the early times of Pd/carbonates chemistry. Formation of cyclopropanes is reversible nnder Pd(0) catalysis and further cycloadditions with electronically poor olefins or aryl isocyanates were reported. This will be... 

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