1.3- Cycloalkadienes

Alicyclic Hydrocarbons. These refer to cyclic analogues of aliphatic hydrocarbons and are named accordingly, using the piefix cyclo-." Their properties are similar to their open-chain aliphatic counterparts. Alicyclic hydrocarbons are subdivided into monocyclic (cycloalkanes, cycloalkenes, cycloalkynes, cycloalkadienes, etc.) and polycyclic aliphatic compounds. Monocyclic aliphatic structures having more than 30 carbon atoms in the ring are known, but those containing 5 or 6 carbon atoms are more commonly found in nature [47, p. 28]. 

Keywords stereoelectronic effects, steric effects, alkadienes, cycloalkadienes... 

Ibata T. Diels-Alder Reactions of AcycUc and AUcycUc Dienes in Org. Synth. High Pressures 1991 213, Eds. Matsumoto K., Acheson R. M., Pb. Wiley N.Y. Keywords hefera-Diels-Alder reactions, alkadienes, cycloalkadienes, high pressure... 

Endoperoxides 6 are readily available via singlet oxygenation of the corresponding 1,3-cycloalkadienes 5 (Eq. 4)13). 

These consist of three types cycloalkenylalkanes, cycloalkadienes, cycloalkynes, etc. (unsaturation in the ring), cycloalkylalkenes,. (unsaturation in the side chain) and cycloalkenylcycloalkenes (unsaturation in both ring and side chain). Example 2-cyclohexyl-2-(cyclohexen-3-yl)propane. 

C. Deprotonation of Bicyclo[3.2.1]alkadiene, Some Other Cycloalkadienes and Cyclooctatetraene Bishomoaromaticity and Transannular Cyclization... 

In the case of 1,3-butadiene, the chemical shifts of inner (H2, H3) protons and outer (HI, H4) is large, while in the case of cycloalkadienes (e.g. 1,3-cyclopentadiene and 1,3-cyclohexadiene), the difference is very small. It is interesting to note that in 1,3,5-cycloheptatriene, the chemical shifts of three kinds of olefinic protons are very diverse. The effect of the ring size and in the chemical shifts of radialenes was also included. 

Nevertheless, a different selectivity has really been observed83 in bromofluorination reactions of 1,5-cycloalkadienes with NBS/Et3N-3HF or Olah s reagent. The reaction of 1,5-cyclooctadiene (3) with the former reagent yields mainly the 1,2-addition product 52, but when the reaction is carried out with Olah s reagent only compounds 53 and 54, arising from the usual transannular jr-cyclization, are formed (equation 53). 

Under the conditions which cause migration of the double bonds, e.g. treatment with sodium and especially potassium, the isolated double bonds can become conjugated, and thus they undergo reduction by metals. Some macrocyclic cycloalkadienes were reduced (predominently to trans cycloalkenes) by treatment with potassium on alumina in a hydrogen atmosphere [350]. 

Good results were also obtained in the Diels-Alder reactions of methyl 2-chloro-2-cyclopropylideneacetate (1-Me) with cycloalkadienes. Thus, 1-Me reacted with cyclopentadiene within 5 h at ambient temperature to give endo/exo-... 

Depending on the reaction conditions, alkenes may undergo either of two types of catalytic polymerization. The products of the first type, which may be termed true polymerization, consist of alkenes having molecular weights which are integral multiples of the monomer alkene. The second type, conjunct polymerization, yields a complex mixture of alkanes, alkenes, alkadienes, cycloalkanes, cycloalkenes, cycloalkadienes, and, in some cases, aromatic hydrocarbons the products do not necessarily have a number of carbon atoms corresponding to an integral multiple of the monomer. 

Alkadiene und 1,3-Cycloalkadiene reagieren mit N,N -Bis-[4-methyl-benzolsulfonyl]-selendiimid (in situ aus Selen und Chloramin-T in Dichlormethan) und 4-Methyl-benzol-sulfonsaure-amid unter Bildung von 3,4-Bis-[4-methyl-benzolsulfonylamino]-alkenen, wahrscheinlieh fiber eine [4+2]-Cycloaddition3. 

Volume ElOc — F2 - F —Alkadienes, F —Polyene, F — Bicycloalkenyls. F —Cycloalkadienes... 

Volume ElOc From Fluoro-alkadienes or -cycloalkadienes 1679... 

The few data available on conjugated dienes indicate that 1,3-cycloalkadienes undergo 1,2 addition,32 and acyclic dienes yield isomeric allylic alcohols resulting from 1,2 and 1,4 addition.33... 

Since the products are optically active, this excludes the symmetric, resonance-stabilized allylic ion intermediate. The main (treats) product arises from the preferential attack of Br- on the more stable, less strained, partially bridged 30 intermediate (as compared to 31). Similar conclusions were drawn from the results of the iodination and haloiodination of 2,3-pentadiene256 and from bromination of 1,2-cycloalkadienes.257... 

Cycloalkadienes exhibit a similar behavior. Thorough studies by Backvall and coworkers576 revealed that the proper choice of ligand permits regio- and stereoselective 1,4-difunctionalization. LiCl and LiOAc were found to exhibit a profound effect on the stereoselectivity 577... 

Cycloalkenes and cycloalkadienes are about as reactive chemically as their open-chain analogs. Cycloalkenes can undergo addition reactions in which the double bond is eliminated and also can undergo cleavage reactions which cause the ring structure to be opened into a chain. 

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