Dimeric alkenes

Aldehydes and ketones, both aromatic and aliphatic (including cyclic ketones), can be converted in high yields to dimeric alkenes by treatment with TiCl3 and a zinc-... 

Desulfuration-dimerization of dithioketals.1 Dithioketals when refluxed with W(CO)6 in chlorobenzene are converted into the corresponding dimeric alkenes. 

Problem 6.37 Write the structural formula for (a) the major trimeric alkene formed from (CH,)2C=CHj, labeling the mer (b) the dimeric alkene from CH,CH=CH2. [Indicate the dimeric R. [ ... 

Dimeric alkene complexes, in which two formal Zr(III) units are bridged by an alkene, have been prepared. Some ethylene complexes have been characterized by X-ray analysis [Cp2ZrClAlEt3]2(p-CH2CH2) [101], [Cp2ZrMe]2(p-CH2CH2) [102] and [MX3(PEt3)2]2(p-CH2CH2) (M = Zr, Hf X = Cl, Br) [103]. 

Reductive dimerization. Alkenes, which are geminally substituted with two activators, undergo dimerization at the (3-position. Cyclization follows. 

Dimeric alkenes from stabilized W water, the reaction proceeds by a single t cal dimerizes, and the dimer loses two... 

None of the chlorophosphetane is produced in the absence of the AICI3, and the amount of the latter employed has a marked influence on the product yield thus if the ratio of the three reactants alkene, PCI3 and AICI3 was 1 1 0.75 the yield was about 50%, the yield was about 80% if the ratio was 1 1 1 and > 95% if it was 1 1 1.25. Replacement of the dichloromethane solvent by either a pure aliphatic or aromatic hydrocarbon prevented phosphetane formation, and the use of 1,2-dichloroethane gave some phosphetane together with some dimerized alkene. 

It was soon established that singlet and triplet forms of carbenes could interconvert . The singlet form underwent reactions such as reacting with water to yield alcohols and with alcohols to yield ethers, while the triplet form lead to dimerization reactions such as azine and dimeric alkene formation. 

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