2,4-Heptadiene

This procedure illustrates a general method for the preparation of 2-hydroxybicyclo[3.2.0]heptanes by copper(I)-catalyzed photobicyclization of 3-hydroxy-1,6-heptadienes, and a general route to the requisite dienes from allyl alcohols by conversion to 4-pentenals and treatment of the latter with vinyl Grignard reagents. 

A 1990 patent reported the quantitative cydization of 1,5-hexadiene 66 to 67 with Cp 2LuCH3 (Cp = C5Mc5 anion) in the presence of PhSiH3 (Scheme 14) [39]. This result was followed by reports that Cp 2NdCH(SiMe3)2 reductively cyclized both 66 and 1,6-heptadiene (68) under similar conditions [40] and that Cp 2SmCH(SiMe3)2 also served as a precatalyst for the cydization of 1,5-hexadiene [41]. In the case of the neodymium and samarium catalysts competitive alkene hydrosilylation was observed. 

See 4-Hydroxy-4-methyl-1,6-heptadiene Ozone See other OZONIDES... 

Chemical Name 1,6-heptadiene CAS Registry No 3070-53-9 Molecular Formula C7C12 Molecular Weight 96.170 Melting Point (°C) ... 

Acyclic dienes as 1,6-heptadienes can be converted to bicyclic compounds, e.g. bicyclo[3.2.0]heptanes, in the presence of cuprous triflate (4.36) 439). 

Asymmetric Cyclizations of 1,6-Heptadiene and of Diallyl Ether Using Catalyst Modified with Epimers of MENTHYL-rerf-BuTYLMETHYLPHospHiNE... 

Shevlin and coworkers30 studied the radiolysis-induced addition of the a-hydroxy isopropyl radical to substituted 1,6-heptadienes and analogs containing a heteroatom. The radical was generated by /-irradiation of propanol solutions of various 1,6-heptadienes. It was found that the adduct to the double bond decomposed to give a compound containing a five-membered ring (equation 26). 

Free-radical chain reactions have been reviewed60. The cyclization of dienes by the action of free radicals is illustrated for the case of the 1,6-heptadiene derivative 90 (E = CC Me) in equation 56. Treatment with tosyl radicals, produced from tosyl chloride and a catalytic amount of dibenzoyl peroxide, generates the radicals 91, which cyclize to 92. The latter reacts with tosyl chloride to form 93 and tosyl radicals are regenerated. The product is obtained in 85% yield as a 6 1 mixture of cis- and fraws-isomers61. 

The action of a catalytic amount of triethylborane on tris(trimethylsilyl)silane induces the formation of tris(trimethylsilyl)silyl radicals, which promote the ring-closure of 1,6-heptadiene to a mixture of the cis- and rirms-cyclopcntanc derivatives 115, together with a small amount of the silicon heterocycle 116 (equation 61)68. 

Diisobutylaluminium hydride catalyses the ring-closure of various dienes. It is proposed that the process involves addition of the aluminium hydride to a terminal double bond, followed by ring-closure and, finally, elimination of the catalyst (equation 106). Thus 1,5-hexadiene gives methylenecyclopentane (213) (equation 107), 1,6-heptadiene gives methylenecyclohexane (214) (equation 108), 4-vinylcyclohexene gives bicyclo[3.2.1]oct-2-ene (215) (equation 109) and the spiro compound 217 is obtained from 5-methylene-l,8-nonadiene (216) (equation 110)112. 

Heptadiene and zirconocene, generated from zirconocene dichloride and butyllithium, form an intermediate, presumably the metallocycle 222, which is transformed into fraws-l,2-di(bromomethyl)cyclopentane (223) by the action of bromine at —78°C. In contrast, a similar reaction of 1,6-heptadene with Cp ZrCl (Cp = pentamethylcyclopentadienyl) (from Cp ZrCl3 and sodium amalgam) gives solely the c -isomer 225 via the complex 224 (equation 114)117. 

The metal-catalysed olefin metathesis (equation 122) when applied to dienes results in ring-closure and expulsion of an olefin (equation 123). Thus the molybdenum carbene complex 241 promotes the decomposition of the 1,6-heptadiene derivative 242 to a mixture of the cyclopentene 243 and ethylene (equation 124)122. An analogous reaction of the alcohol 244 gives 245 (equation 125), and 4-benzyloxy-l,7-decadiene (246) affords the cyclohexene 247 and 1-butene (equation 126). These transformations, which occur in benzene at room temperature, proceed in excellent yields122. 

The use of 1,6-diene systems usually does not result in cyclization reactions with palladium ) salts. For example, with 1,6-heptadiene a /i-elimination takes place from the cqjr-intermediate to give diene 22 as the major product (equation 10)27. However, more recently Trost and Burgess21 have shown that with a 4,4-bis(phenylsulfonyl) derivative of 1,6-heptadiene (23) an insertion takes place to give a 5-membered ring product (24, equation 11). The final step of the latter reaction is oxidative cleavage of the palladium-carbon bond by CuCl2 to produce a carbon-chlorine bond. 

Cyclopolymerization of Nonconjugated Dienes. Cyclopolymerization is an addition polymerization that leads to introduction of cyclic structures into the main chain of the polymer. Nonconjugated dienes are the most deeply studied monomers for cyclopolymerization and for cyclocopolymerizations with alkene monomers 66 In general, (substituted and unsubstituted) dienes with double bonds that are linked by less than two or more than four atoms cannot undergo efficient cyclization and result in crosslinked materials.12 In fact, efficient cyclopolymerization processes have been described, for instance, for a,oo-dienes like 1,5-hexadiene, 2-methyl-l,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene,67 73 which lead to formation of homopolymers and copolymers containing methylene-1,3-cycloalkane units. 

Diastereoselective iodolactonization of y, -unsaturated acids.2 Kinetic io-dolactonization of the meso-1,6-heptadien-4-carboxylic acid (1) results in two prod-... 

Reaction of iodine with non-conjugated dienes has been applied to the synthesis of cyclic compounds100. Although the reactions of 1,5-hexadiene, 1,6-heptadiene and 1,7-octadiene with I2 in CCI4 gave exclusively products arising from addition to the two double bonds, the introduction of dialkyl substituents into the 4-position of 1,6-heptadiene completely changed the reaction course in favor of cyclization (equation 85). 

Carbocupration of alkynes by zirconacyclopentane derivatives can be performed according to the same procedure. Thus, the zirconocyclopentane 135, obtained by treatment of Bu2ZrCp2 with 1,6-heptadiene, reacts at room temperature with phe-nylacetylene to afford the adduct 136 through a carbocupration-reductive elimination mechanism. Cross-coupling followed by intramolecular carbocupration takes place in the case of the reaction with 1-bromohexyne, producing 137 (Scheme 2.66) [143]. 

Cyclic olefins and diolefins form much more aerosol than 1-alkenes that have the same number of carbon atoms (for example, cyclohexene 1-hexene, and 1,7-octadiene 1-octene). The same effect of chain length and double-bond position is observed for diolefins (1,7-octadiene > 1,6-heptadiene > 1,5-hexadiene, and 1,7-octadiene 2,6-octadiene). Heavier unsaturated cyclic compounds, such as indene and terpenes, form even more aerosol. 

Cyclic olefins and diolefins form aerosol even when present at very low concentrations, as confirmed by smog-chamber studies for cyclo-hexene and 1,6-heptadiene. ... 

FIGURE 3-21 Threshold concentration for aerosol formation with 1,6-heptadiene. Reprinted with permission from O Brien et td. 

Methyl 2-bromo-2-cyclopropylideneacetate (11a) has never been tested in these reactions, but has been used as a starting material for the stepwise construction of 1,6-heptadienes with methylenecyclopropane units for intramolecular Heck reactions. Thus, bromo ester 11a, after reduction, subsequent conversion of the resulting alcohol to the bromide and coupling with enolates of substituted malonates, was transformed into dienes of the type 254 (Scheme 73) - versatile synthetic blocks for the preparation of functionally substituted spirocyclopropanated bicyclo[4.3.0]nonenes 255a-d by a domino Heck-Diels-Alder reaction [122a]. 

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