The regioselectivity in cyclofunctionalization of some acyclic olefinic alcohols with benzeneselenenyl halides (PhSeCl and PhSeBr) at different temperatures ( -78"C, 0°C and room temperature) is investigated. It has been found that A*and A5-alkenols are converted into five-and/or six-membered cyclic phenyl selenoethers, the yield of which decreases with increasing reaction temperature. PhSeCl has been found to be more efficient than PhSeBr in the cyclization reactions.Electrophilic organoselenium reagents (i.e. PhSeX) readily add to olefinic bonds (A, Scheme 1). Presumably, the selenonium intermediate B is formed, which suffers external trans-nucleophilic attack by X-to give the substituted selenide C. On the other hand, intramolecular capture of the selenonium species B by an internal nucleophilic oxygen, results in the formation of a ring, affording Markovnikov (D) and/or anti-Markovnikov products (E)[5,61. C EMarkovnikov product Anti-Markovnikov product

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1‐Alkenes are converted in high yields to the corresponding primary diorganomagnesium compounds by transition metalcatalyzed hydromagnesation reaction using catalytically prepared suspended (MgH2*) or dissolved magnesium hydride (MgH2*). The most active hydromagnesation catalysts have been found to be combinations of zirconium tetrahalides with MgH2* or MgH2*. The reaction is highly regio‐and chemoselective. The diorganomagnesium compounds prepared in situ from magnesium, hydrogen, and 1‐alkenes can be applied to the synthesis of organic and organometallic compounds just as Grignard compounds (Scheme 3, reaction 3–11). Dioctylmagnesium undergoes the growth reaction with ethene in the presence of quinuclidine and is oxidized by molecular oxygen in high yield to 1‐octanol.

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Reactions of some primary and secondary A4-r A5and A6-alkenols with thallium triacetate (TTA) in benzene, acetic acid and chloroform as solvent have been investigated. When terminally unsubstituted A4-alkenols, such as 4-penten-1-01 (5a) and 5-hexen-2-01 (5b), are treated with TTA in benzene, pacetoxylated tetrahydrofurans 8a and 8 b are obtained. However, when the reaction is carried in acetic acid the products are both regioisomers, i. e. five-and six-membered cyclic ethers (8a, 8b, 7a and 7b). 4-Methyl-4-penten-1-01 (5c) is converted in benzene into a mixture of products (8c and 7c) in which the tetrahydropyran derivative 7 c is predominant, and in acetic acid it is the sole cyclization product. Terminally dialkylated alkenols, such as 5-methyl-4-hexen-1-01 (1 b) and