Iodo acetates, from alkenes

Pans-2-Iodocyclohexyl acetate can be isolated in essentially quantitative yield from the reaction of thallium(I) acetate, iodine, and cyclohexene in a 1 1 1 molar ratio in refluxing chloroform. lodo acetates from a representative series of alkenes including cyclohexene have been similarly prepared in 80-98% yield in glacial acetic acid which was not dried as described in this procedure. The corresponding iodo benzoates are obtained in comparable yields from reaction with thallium(I) benzoate and iodine in benzene. The deactivated olefin methyl cinnamate did not react under these conditions, and o-allylphenol underwent ring iodination to... 

Allyltitanium complexes derived from a chiral acetal have been reacted with carbonyl compounds and imines [63], While the chiral induction proved to be low with carbonyl compounds, high induction was observed with imines. This complex represents the first chiral homoenolate equivalent that reacts efficiently with imines. Finally, the reactions with electrophiles other than carbonyl compounds and imines, namely a proton source, NCS, and I2, furnished the corresponding alkene, chloro, and iodo derivatives in good yields [64]. 

The regio- and stereochemistry of the addition to 1-phenylcyclohexene was shown by H-, 13C-and 1SN-NMR studies22 23. Solvolysis of ir A-l-azido-2-iodo adducts 1, prepared from cyclohexene and 1-methyl- and 1-phenylcyclohexene with silver acetate in acetic acid, gave fi-azido acetates 2-4 in excellent yield the regioselectivity and the stereoselectivity of this transformation is dependent on the nature of the alkene substituent R14,15,23. 

The dipolar cycloaddition of an alkyl azide with an alkene to form an aziridine has been exploited in the total synthesis of the alkaloid ( )-aspidospermidine <20050BC213>. Enone 353 was prepared in 11 steps from 3-ethoxycyclohexenone and coupled to 2-iodo nitrobenzene under Ullman cross-coupling conditions. The acetate group of 354 was hydrolyzed and the resulting alcohol converted to an azide using standard conditions in 75% overall yield. The cycloaddition of the azide with the enone was conducted in refluxing benzene for 3 days. The fused-ring aziridine 355 was the only product isolated. None of the initial dipolar cycloadduct triazoline was observed. The... 

The cisjtrans ratio of the cyclopropanes formed in this transformation depends to some extent on the nature of the salts and the solvent. A particularly high cisitram ratio was obtained when copper(II) acetate, calcium chloride, and ethanol were employed (no values given). Cyclopropane synthesis from active methylene compounds and nonactivated alkenes was also possible with the help of iodine and a base under phase-transfer conditions. Intra-and intermolecular reactions to give 6 and 5, respectively, have been carried out. The intramolecular reaction is nonstereospecific with respect to the C-C double bond. Although an iodo-substituted intermediate has been isolated in one case, all the details of the reaction mechanism are not yet clear. 

Because detailed mechanistic information is not available, a tentative mechanism is proposed here. It is assumed that iodine first adds to the double bond to form an iodonium cation in a process similar to the bromination of alkene, then nucleophilic attack from acetate leads to the formation of the ra/25 -o -iodoacetate. In the presence of silver acetate, a-iodo leaves to give a dioxoanyl carbocation, which is attacked by the second acetate anion to give 1,2-diacetate. Upon hydrolysis or LiAlH4 reduction, diacetate is transformed into trans-l,2-diol. The displayed mechanism is similar to the one proposed by Sudalai. ... 

In Chapter 19 reference is made to a 2, 3-unsaturated nucleoside being hydroxylated to a ribofuranosyl compound which then, via the 5-deoxy-5-iodo-analogue was converted into the 5-deoxy-4-enofuranosyl nucleoside. A compound with a related alkene system has been obtained from an L-sorbo-furanose acetal (Scheme 11). [cf. Compound (2) above.]... 

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