L,13-Dien-7-ynes

Nonetheless, there are a small number of systems that do mediate such [2 -i- 2 -t- 2] cycloadditions. With allenes as the alkene , cycloaddition with both acetylene and terminal alkynes proceeds regio-selectively to give 3,5-dimethylenecyclohexenes using Ni catalysts, and mostly 3,6-dimethylenecyclo-hexenes using Ni° catalyst precursors (equation 19). Norbomadiene undergoes so-called homo-Diels-Alder cycloaddition with both alkenes and a ynes in the presence of nickel catalysts. Further elaboration of this chemistry with alkynes but not alkenes has been described using a Co/Al catalyst system (equation 20). Attempts to produce cyclohexenes via all-intramolecular [2 + 2 + 2] cycloaddition of l,13-dien-7-ynes or 1,1 l-dien-6-ynes have been unsuccessful. ... 

An interesting sequence of two consecutive Heck-type cyclizations and a subsequent Diels-Alder addition was observed when the methoxycarbonyl-substituted 2-bromo-trideca-1,1 l-dien-6-yne ( /Z)-63 was treated with the typical palladium catalyst (Scheme 3-20) [172]. The cyclization of dienyne 63 at 80 °C gave two diastereomeric trienes ( /Z)-64. At higher temperature (130 °C), an intramolecular Diels-Alder reaction of only the ( J)-isomer ( )-64 occurred to give the tetracyclic 65, whereas (Z)-64 remained as such, probably due to steric interference of the methoxy group. 

Domino cyclizations of various types of polyenynes offer powerful synthetic tools for efficient syntheses of polycyclic compounds. Among many possibilities, several representative patterns are cited here. A fully intramolecular version of a three-step domino reaction of 2-bromododeca-l,l l-dien-6-yne 184 and 2-bromotrideca-l,12-dien-7-yne 189 offers a useful synthetic method of the tricycles 188 and 191 with a central cyclohexa-1,3-diene moiety. In these compounds 184 and 189, an alkenyl bromide starter, an alkynyl relay, and an alkenyl terminator are all tethered as summarized by 184 in Scheme 3.14. The final step is facile 6- 7r-electrocyclization of 187 and 190 to give rise to 188 and 191 [61]. 

The same palladium-catalyzed domino cyclization-anion capture sequence involving carbopalladation of allene (69), which was employed by Grigg et al. for the synthesis of diene 70 (Scheme 10) can yield 1,3,5-hexatriene 194, when starting from 2-bromo-l-ene-6-yne 193 instead of the aryl iodide 68 (Scheme 32) [52], Under the conditions of its formation, 194 immediately undergoes thermal 67r-electrocyclization to give the bicyclic product 195. 

In addition to propargylic carbonates, propargylic chlorides react with terminal alkynes in the presence of triethylamine or diisopropylamine. 5-Butyldodeca-3,4-dien-6-yne (165) was obtained in 91% yield by the reaction of 3-chloro-4-nonyne (164) with 1-heptyne in diisopropylamine (Section 11-45). Coupling of the propargylic acetate 166 with 1-heptyne is possible in the presence of three equivalents of zinc chloride with or without cuprous iodide to give the l,2-alkadien-4-yne 167 [40]. 

In more complex reaction cascades an additional alkyne-insertion step can occur. Thus starting with intramolecular carbopalladation of a vinyl iodide to a carbon-carbon triple bond, followed by two intramolecular alkene-insertion steps and termination with dehydropalladation, a palladium-catalyzed synthesis of l-(5 -methylbicyclo[3.1.0]hex-T-yl)-5,5-bis(carboethoxy)cyclo-hexadiene (52) starting from l-iodo-4,4-bis(carboethoxy)-ll-methyldodeca-l,ll-dien-6-yne (51) is achieved. ... 

Another potentially powerfnl sequence arises by combining one or two intramolecular Heck-type couplings with an intra- or intermolecular Diels-Alder addition (for early examples of inter-intermolecular one-pot domino Heck-Diels-Alder reactions see Refs. [49] and [50]). An all-intramolecular version of such a sequence has been shown to proceed reasonably smoothly for terminally alkoxycarbonyl-substituted 2-bromotrideca-l,ll-dien-6-ynes under palladium catalysis at 130 °C. At 80 °C, the sequential reaction stops after the two consecutive Heck-type cyclizations and subsequent /3-hydride elimination to give a 1,3,6-triene apparently only the ( )-isomer undergoes the intramolecular Diels-Alder reaction, as the (Z)-l,3,6-triene is observed accompanying the tetracyclic system obtained at 130 °C (Scheme 36). 

Palladium catalyzed cycloisomerizations of 6-cn-l-ynes lead most readily to five-membered rings. Palladium binds exclusively to terminal C = C triple bonds in the presence of internal ones and induces cyclizations with high chemoselectivity. Synthetically useful bis-exocyclic 1,3-dienes have been obtained in high yields, which can, for example, be applied in Diels-Alder reactions (B.M. Trost, 1989). 

Reaction of pyridazine 1-oxide with phenylmagnesium bromide gives 1,4-diphenyl-butadiene as the main product and l-phenylbut-l-en-3-yne and 3,6-diphenylpyridazine as by-products, while alkyl Grignard reagents lead to the corresponding 1,3-dienes exclusively (79JCS(P1)2136>. 

However, 2-bromotetradeca-l,13-dien-7-ynes such as 96 n = 1), which were set up to furnish decahydrophenan-threne skeletons (6-6-6-tricycles), gave the interesting tetracyclic compounds 97 (n=l) with a cyclopropane moiety bridging the A- and B-ring junction (Scheme 27). " " ... 

In the next step, 3 could insert into one of the C H bonds of 1 to provide vinylacetylene (4, butenyne), a compound that is indeed generated when 1 is pyrolyzed. Repetition of the carbene formation step could then produce 5, which, by another insertion step, would lead to hexa-l,3-dien-5-yne (6, mixture of isomers). This is already an isomer of benzene, and that it can cyclize to 2 was shown by us many years ago [6]. Obviously, 6 could also be a precursor of styrene and other oligomers of 1. The mechanism proposed in Scheme 2 could also be of importance in connection with soot formation from smaller hydrocarbon fragments, and account for the formation of 2 in interfeller space. 

Tetraacetylenes such as 115 and 116 contain the 1,5-hexadiyne group as a bridging element. Since the base-catalyzed isomerization of this unit to hexa-l,3-dien-5-yne (6) constitutes the basic reaction of Sondheimer s annulene chemistry [75], it appeared attractive to attempt to apply this classic reaction of planar aromatic chemistry to a layered precursor and create three-dimensional relatives of Sondheimer s dehydroannulenes. Indeed, both 115 and 116 could be isomerized to their fully conjugated isomers 129 and 130, respectively, by treatment with potassium tert-butoxide in tert-butanol, the original Sondheimer conditions (Scheme 28). From the X-ray structure obtained for 130, it was concluded that both hydro-... 

All-c/5-l,6-dichloro-l,3,6,8-cyclodecatetraene (123) and all-cw-l,6,6-trichloro-1,3,8-cyclodecatriene (124) were obtained by the reaction of c/j,c/j-3,8-cyclodeca-diene-l,6-dione (122) with phosphorus pentachloride . Treatment of 123 with lithium diisopropylamide led to all-cij-l-chloro-l,3,8-cyclodecatrien-6-yne (125) and naphthalene (126). The same products (125 and 126) were obtained by a similar... 

In enynes, both the double and the triple bond can compete for the carbenoid that is generated from alkyl diazoacetate under copper or rhodium catalysis. The chemoselectivity is sometimes not very pronounced, but but-l-en-3-yne is selectively attacked at the triple bond [methyl diazoacetate, RhjCOAc), 70% yield], whereas in 2-methylhexa-l,5-dien-3-yne only the double bonds accept the carbenoid (Table 12, entry 2). The vinylcyclopropene obtained by addition to the triple bond may dimerize to form a 3,6-dialkoxycarbonyltricyclo-[3.1.0.0 ]hexane.2 "... 

An alkynylcyclopropane was also formed on heating a 10-selena-l 1,12-diazatricyclo[6.3.0.0 ]-dodeca-l(9),ll-diene under reduced pressure to give bicyclo[6.1.0]oct-2-yne in 21% yield. When the thermolysis was carried out in the presence of 2,3,4,5-tetraphenylcyclopenta-2,4-dienone, the alkyne underwent a Diels-Alder reaction subsequent decarbonylation gave 10,11,12,13-tetraphenyltricyclo[6.4.0.0 ]trideca-l (9),10,12-triene. ... 

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