Intramolecular alkoxycarbonyl carbonate

Through an intramolecular alkoxycarbonylation reaction catalyzed by palladium(II), 4-pen-tenc-l,3-diols give tetrahydrofuro[3,2-6]furan-2(3f/)-ones. The reaction is carried out by treating the unsaturated diol with palladium(ll) chloride, copper(ll) chloride and sodium acetate under a carbon monoxide atmosphere. The yields are good and five-membered rings are exclusively obtained with total regioselectivity, as shown by the cyclization of. sj -3-hydroxy-melhyl-5-hexene-l,4-diol (1), which affords only one product in 60% yield44. 

Chiusoli and co-workers succeeded in preparing furan-2-acetic esters by Pd-catalyzed intramolecular alkoxycarbonylation of (Z)-2-en-4-yn-l-ols under oxidative conditions (Scheme However, a high carbon monoxide pressure (up to 100 atm) and an ex-... 

The phthalide structure of mycophenolic acid ]88] and phthalideisoquinoline alkaloids [89] were constructed by intramolecular alkoxycarbonylation of substituted 2-bromobenzyl alcohols as substrates. Similar compounds were obtained by employing in situ generated carbon monoxide obtained from solid Mo(CO)6 under micro-wave irradiation [90]. 

Shinto, T., Tajima, f., Suishu, T., and Somekawa, K. (1991) Intramolecular photochemical reactions of 4-(alkoxycarbonyl group at the olefinic carbon chain. Journal of Organic Chemistry, 56, 7150-7154. 

The spectra of 2-alkoxycarbonyl-3-aminoacrylic esters (73, R1 = H, alkyl, aryl) show that these substances exist in the enamino-ester form with a strong intramolecular hydrogen bond between the amino and COOR2 groups. Conformers 73a (Z, Z, E) and 73b (E,Z,E) predominate in non-polar media conformation 73b is also probably present in polar solvents and is preferred in the solid state109. (The symbols indicate, in the order shown, the alignments of the free C=0, the bonded C=0 and the R1 group with respect to the carbon-carbon double bond.)... 

A useful extension of the alkoxycarbonylation reaction has been devised in order to obtain 3,4-dihydro-4-hydroxy-l//-2-benzopyran-3-acetic acid lactones from 5-alkene-l,4-diols. The intramolecular cyclization of 7, carried out with palladium(II) acetate and copper(II) chloride under a carbon monoxide atmosphere, affords the m-lactone 8 in 68% yield. The configuration is assigned on the basis of H-NMR double resonance methods86. 

Intramolecular acylation. When a carbonate ester containing an alkyne or allene unit" at the proper length is submitted to i-PrMgBr/( -PrO)4Ti, the multiple bond is metallated and becomes nucleophilic such that internal attack on the carbonyl group results in O —> C transfer of the alkoxycarbonyl group. Diethyl alkynyhnalonates also undergo a similar reaction. ... 

Described in this section are a couple of reports on the synthesis of 5-lactones wherein the ring closure has been achieved through a radical cyclization. Bachi and Bosch have reported the synthesis of 5-lactones by free-radical annelation of phenylselenyl carbonates [103] (Scheme 58). An intramolecular addition of an alkoxycarbonyl radical, formed by reaction of phenylselenyl carbonates 275 with tri-n-butyltin hydride in the presence of AIBN, to carbon-carbon multiple bonds provided the highly substituted lactone 276. The salient features of this free-radical cyclization include high regioselectivity favoring exo addition and a high ratio of cyclization to reduction products. 

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