Iodonium nitrate in chloroform-pyridine at room temperature undergoes a trans stereospecific electrophilic addition to alkenes to form ( i ) iodoaliphatic nitrate esters, (ii) iodoalkane pyridinium nitrates, or (iii) alkene pyridinium iodides depending on the substrate. The addition is sensitive to steric hindrance effects and anti-Markovnikov addition is commonly encountered. In similar additions to conjugated dienes 1,2-additions in a Markovnikov fashion to form 1 :1 adducts of type (ii) are the rule. Terminal acetylenes give alkynyl iodides in fair yield.Canadian Journal of Chemistry, 49,403 (1971) Investigations of the scope and mechanism of addition of pseudo-halogens (iodine isocyanate, iodonium azide, nitrosyl acetates, N,N-dichlorourethan) have attracted considerable attention and ha;e proved of synthetic utility in the preparation of aziridines and P-halocarbamates (1-7). , ,In a preliminary communication we reported the addition of iodonium nitrate (generated in situ bv the reaction of iodine chloride with silver nitrate in chloroform-pyridine solution) to some monoolefins, a reaction which gave (i) iodoaliphatic nitrate esters, (ii) iodoalkane pyridinium nitrates, or (iii) alkene pyridinium iodides depending on the substrate (8). These reactions extended the range of known pseudo-halogen additions and complemented the recent report by Hassner et al. of the reaction of nitryl iodide with alkenes..(9).In a continuation of our investigations we report reactions of iodonium nitrate with (a) dienes, conjugated and unconjugated, cyclic and acyclic; (b) acetylenic compounds; and we provide further details ofthe reactionswith(c)acyclic and cyclic alkenes, terminally and nonterminally unsaturated. Reactions with Acyclic Terminal AlkenesSimple alkenes upon reaction with iodonium nitrate gave only products of the type shown in eq. 1. Only in the case of 1-hexene however was 'Research Council of Alberta Contribution No. 498. the adduct predicted from considerations of carbonium ion stability (i.e. corresponding to Markovnikov addition) the sole product in the reaction, when 1-iodo-2-hexanol nitrate was produced in 83% yield. This and similar structures were confirmed by zinc-copper couple reduction, followed by treatment of the resulting iodohydrin with lithium aluminum hydride (procedure A, see eq. 2). The alcohol produced was identical with an authentic sample of 2-hexanol.Steric factors appear to play an important role directing the approach of the nitrate ion to the initially formed iodonium ion in the case of 3,4-dimethyl-I-hexene leading to a mixture of 70% Markovnikov and 30% anti-Markovnikov2 addition (see Table 4). In the assignment of structures to these and similar products in this study by n.m.r. spectroscopy it was observed that methine protons alpha to an ONO, group absorb in the range 4.8-5.4 6, whereas protons alpha to an iodo function absorb in the range 4.C5.0 6 (10). Fowler et al. have shown that methylene protons alpha to an iodo function absorb at 3.0-3.5 6 (1 1). In our work methylene ...

lodonium nitrate in pyridine-chloroform at room temperature undergoes preferential electrophilic addition to certain olefinic alcohols to form (i) hydroxyiodoalkyl nitrates and (ii) hydroxyiodoalkylpyridinium nitrates. Parallel reactions in sym-collidine-chloroform gave three-, four-, and five-membered cyclic ethers as well as products of type

A series of 2-alkoxy- and 2-aryloxy-tetrahydropyrans has been hydrogenolyzed in ether by LiAlH4–AlCl3. As the alkyl group attached to the exo oxygen atom is changed from primary to tertiary, the proportion of ring cleavage to side-chain cleavage increases. Only side-chain cleavage occurs with the 2-aryloxytetrahydropyrans. The results are explained in terms of the polar properties of the alkyl or aryl group attached to the ring oxygen or the side-chain oxygen. Any control by steric factors is considered to be submerged by the polar effects, but does have a clearly apparent directive effect when the polar factors are equal for the two routes of cleavage. The results of the hydrogenolysis of 6-substituted 2-alkoxytetrahydropyrans could be explained on the same basis.The configurations of the cis and trans isomers of the disubstituted tetrahydropyrans were determined by nuclear magnetic resonance spectroscopy. Their conformational preference is discussed.

In ether solution, 1,3-diosolanes are hydrogenolyzed faster by LiAII-Id-AlCl3 than are the corresponding 1,3-dioxanes. This difference is attributed to the relative ease of oxocarbonium ion formation in the rate-determining step of the reaction. The results obtained have been utilized to explain the selective cleavage of the five-and six-membered acetal structures found in the polyacetals of hexitols.

The relative ease of hydrogenolysis of ether solutions of acetals or ketals is much greater with AlHzCl than with AlH3. Conversion of the species AlHs & AlHzCl P AlHClz one into the other is fast, and is accomplished by the addition of the appropriate quantity of AlC13 or LiAIH4 to solutions of HlH8 or AlHC12, respectively. Gradual addition of an equimolar proportion of AlCla in ether to an ether solution of equimolar roportions of LiAlH4 and acetal or ketal first forms AlHa, which is rapidly converted into & H~C I as more AlCl3 is added. During the time of this addition (210 min) little reduction by AlH3 takes place. Most of the reduction is done by the species AlHzCl when the AlCl3 is completely added.