Dienyl alcohol

The addition proceeds in three discrete steps and the intermediates can be isolated. Simple alkenes are less reactive than alkynes and do not undergo the addition to aHylic boranes, but electron-rich alkyl vinyl ethers react at moderate temperatures to give 1,4-dienes or dienyl alcohols (440). 

Miscellaneous pheromone components, which are classified as neither Type I nor II, are listed in Table 4. Secondary alcohols with a C7 or C9 chain have been identified from some primitive species i.e., saturated and monoenyl alcohols from three species in Eriocraniidae (Eriocranioidea) [77,78] and dienyl alcohols from one species in Nepticulidae (Nepticuloidea) [79]. Their hydroxyl group is always located at the 2-position, and this is illustrated in the table with the abbreviation 2-OH in place of the OH which was used for the Type I pheromones. Furthermore, esters between a long chain acid and a rather small alcohol have been characterized from species in Tineoidea and Zygaenoidea. Phero-... 

INAS reactions of carbonates of 3,5-dienyl alcohols (i. e., involving a conjugated diene moiety) [72] and 3,4-dienyl alcohols (i. e., having an allene moiety) [73] also proceed smoothly to furnish the corresponding (3,y-unsaturated esters. The reaction of 4-silyl- or 4-stannyl-3,4-dienyl carbonate having axial chirality proceeds with excellent chirality transfer, as exemplified in Eq. 9.39, thereby affording a novel access to optically active a-substituted p.y-unsaturated esters [73],... 

A similar result obtained with nopadiene is presented above (Scheme 13.9). Linear and cyclic trienes furnish alkenyl-r 3-allyltitanium complexes, which can react with aldehydes to produce dienyl alcohols (Scheme 13.13) [24],... 

Some reactions via intermediate alkylideneallyl cations have been reported. Solvolysis of 3-bromo-2,5-dimethyl-2,4-hexadiene in ethanol at 100 °C for 80 min gives 5-ethoxy-2,5-dimethyl-2,3-hexadiene in quantitative yield (Scheme 2) (5). This indicates that ethanol selectively attacks the sp2 carbon of the intermediate alkylideneallyl cation. A similar selectivity has been observed in the solvolysis of 2,3-dienyl alcohols (6), and is in agreement with the charge distribution. A cycloaddition reaction via an alkylideneallyl cation intermediate has been reported as illustrated in Scheme 3(7). 

A new three-component reaction has been made possible by treating an alkenylzir-conium reagent of type 66 with an alkyne 67 and an aldehyde 68 in the presence of catalytic amounts of Ni(cod)2 (10 mol%) and ZnC.F (20 mol%). The resulting penta-dienyl alcohols like 69 are obtained in satisfactory yield. The transmetalation of the... 

Trost used the dihydroxylation methodology extensively in the total synthesis of (+)-parvi-florin (68) [96]. Both bistetrahydrofuran elements were prepared from 8, tn-dienyl alcohol 71. To avoid overoxidation the reaction was stopped before complete conversion, giving triol 72 with 94% ee in 71 % yield. Protection as the acetonide afforded 73 and subsequent hydrogenation furnished saturated alcohol 74. The construction of 75 was accomplished by Julia olefination using derivatives of 73 and 74. Diene 75 was thenregioselectively dihydroxylated at the internal... 

Vinyl epoxides 372 and 373 are converted to conjugated dienes 375 and 378 via the 7T-allyl intermediates 374 and 377. In other words, different protons are eliminated, depending on the structure to give either the cyclopentenone 376 or the dienyl alcohol 378. The unsaturated ketone 376 is an expected product, because elimination of a hydride from the carbon connected to oxygen is common [171]. 

Stereochemistry of the 1,4-eliminative ring opening of [3-substituted ( )-prop-l-enyljoxiranes, e.g. (8), to the corresponding 2,4-dienyl alcohols by LDA has been investigated.31 The results have been rationalized by the syn -effect in the transition state of deprotonation, which mainly arose from a a - n interaction. 

Brown and co-workers developed a novel homoallenyl boronate reagent 169 based on diisopropyl tartrate for the stereoselective homoallenylation of aldehydes 170. The reagent 169 was prepared via homologation of the corresponding allenyl boronate or the alkylation of halomethyl boronate with allenyl Grignard similar to those reported in Scheme 26. The allyl boronate 169 upon reaction with aldehydes furnished the dienyl alcohols 172 with high ee (Scheme 28) <1996JOC100>. 

The PBO catalyst lc was recently applied to the kinetic resolution of allylic alcohols 2e-l by acylation with isobutyric anhydride [18]. The enantioselec-tivity depends strongly on the structure of allylic alcohols and increases with the conformational flexibility of the substrate. The dienyl alcohols 2i-l are good substrates for this kinetic resolution as shown by the high selectivity factors (30-80) obtained (Table 1). 

As shown in racemic series [220], the stereoselectivity of the allylation of chiral 1,3-dioxanes 6.20 depends upon the reaction conditions and upon the nature of the reagent (silane or stannane). The most selective reagent is CH2=CHCH2SnBu3. Most of the reactions have been carried out with trimethyl-allylsilane in the presence of TiC1.4/Ti(0/-Pr)4 under the conditions recommended by Johnson and coworkers [213], After oxidation of the products and treatment with a base, nonracemic homoallylic alcohols are obtained with excellent enantiomeric excesses (Figure 6.58). From CH2=C=CHCH2SiMe3, dienyl alcohols are similarly obtained [1228, 1229] (Figure 6.58). The TiC -catalyzed reactions of dioxanes 6.20 with alkynylsilanes also lead to nonracemic a-alkynyl alcohols [223],... 

Various dienyl alcohols and lactones were amongst the products... 

A boron-tethered (C-B-O) intramolecular Diels-Alder (IMDA) approach has been used to prepare cyclic alkenyl boronic esters 140 (Scheme 19). Thus, reaction of 2equiv of the dienyl alcohol 138 with 137 in THF, in the presence of molecular sieves, provides the corresponding IMDA precursors 139. The IMDS reaction was then accomplished at 190 °C in a toluene solution, with 5 mol% of 2,6-di-fer7-butyl-4-methylphenol as a free radical inhibitor. Transformation of the carbon-boron bond in 140, using standard organoborane reactions, can then afford a variety of functionalized cyclohexene derivatives <1999JA450>. 

Pd-catalyzed reaction of alkenyloxiranes provides two elimination produets, the unsaturated ketones or the dienyl alcohols by elimination of different hydrogens. From eyclopentadiene monoxide (511), the unsaturated ketone 513 was obtained as explained by 512. On the other hand, the dienyl aleohol 516 was obtained from the alkenyloxirane 514 via 515 [194]. 

A useful building block 519 for vitamin D synthesis was prepared by reaction of the alkenyloxirane 517 [195], Under usual conditions of the elimination, both the dienyl alcohol 519 and the unsaturated ketone 520 were formed in equal amounts. Radinov and co-workers discovered an interesting and remarkable effect of the addition of fluorinated alcohols, such as l,3-bis-(l,l,l,3,3,3-hexafluoro-2-hydroxypropyl)benzene or perfluoro-t-butyl alcohol as a proton source, on the chemoselectivity, and the desired 519 was obtained with nearly complete chemos-electivity with these additives [195], They suggest that rapid protonation of the intermediate alkoxide 518 with these alcohols seems to be important. 

Reactive methylene-7r-allylpalladiums 618 are generated from esters of 2,3-aUca-dienyl alcohols 617, and react with nucleophiles to afford either 1,2-dienes 619 or 1,3-dienes 620 regioselectively depending on the nature of allyl leaving groups and nucleophiles. 

The corresponding reaction with 2,3-dienyl alcohols 21 provided a new entry to substituted enal/enone 22, dienal/dienone 23 (Scheme... 

Reaction of palladium complexes with aUcenyloxiranes gives 77-allylpalladium intermediates, which decompose by elimination to give dienyl alcohols or unsaturated carbonyl compounds (Table 5). The selectivity of the elimination depends on the structure of the substratesJ ... 

An intramolecular nucleophile, such as an alcohol, may also be used in place of the first acetate (Scheme 9.77). Treatment of the dienyl alcohol 9.284 with palladium acetate gives the T -allyl complex 9.285 by intramolecular nucleophilic attack, which gives the rran -acetate 9.287 by reductive elimination. In the presence of a small amount of lithium chloride, however, ligand exchange at palladium occurs. Now, the -palladium complex 9.286 does not have an acetate available for intramolecular transfer. Instead,... 

Solvolysis of dienylester complexes generally proceeds stereospecifically to give dienyl alcohol complexes of the same configuration but the ip-endo-ester (12) (R=3,5-dinitrobenzoyl) gives a mixture of both ip-exo- and v - / cfo-isomers whereas the y>-ejtu-isomer of (12) undergoes the normal stereospecific hydrolysis to the y)-exo-alcohol only. An intermediate cation (13) is not involved in the hydrolysis of the... 

The Diels-Alder reaction of ester-tethered trienes is also known as a powerful methodology to construct polycylic Y lactones [68]. Romo et al. [69] surveyed effective organic nucleophilic catalysts for tandem intermolecular Diels-Alder reaction/lactonization reaction of achiral a, 3-unsaturated acid chlorides with dienyl alcohol 100 (Scheme 45). In this case, when chiral Lewis base 102 was used as a nucleophilic catalyst, excellent enantioselectivity was realized. Lipase-catalyzed domino kinetic resolution/intramolecular Diels-Alder reaction of furfuryl alcohols with acrylic acids was also carried out by Akai and Kita [70]. 

In the Diels-Alder reaction of allylic alcohol and dienyl alcohol, Olsson and CO workers reported temporary tethering by aluminum phenoxide (Scheme 6.116) [138]. That is, consecutive addition of diene, dienophile, and 2,6-di-tert-butylphenol to a solution of Me3Al in toluene at room temperature followed by heating at 160 gave a diaster eomeric mixture of cycloadducts in good yield. 

Recently, Georgiadis and coworkers demonstrated temporary tethered Diels-Alder reaction of dienyl alcohol and a-acetoxyacrolein efficiently promoted by MeAlCl2 (Scheme 6.117) [139]. Reaction proceeded with perfect endo selectivity to construct cis-fused oxabicyclo[4.3.0] system. 

Several substituents can be present in the carbon skeleton of 88. The carbonate of 3,5-dienyl alcohol 89 also underwent similar cydization to lead to the corresponding allyltitanium species 90 also having a lactone moiety. This allylic moiety exists most probably as an internal titanium derivative stabilized by intermolecu-lar coordination. The addition of aldehydes leads to the corresponding alcohol via a srx-membered transition state (Scheme 12.60) [78]. 

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