Synthesis with acyclic dienes

For the construction of oxygen-functionalized Diels-Alder products, Narasaka and coworkers employed the 3-borylpropenoic acid derivative in place of 3-(3-acet-oxypropenoyl)oxazolidinone, which is a poor dienophile in the chiral titanium-catalyzed reaction (Scheme 1.55, Table 1.24). 3-(3-Borylpropenoyl)oxazolidinones react smoothly with acyclic dienes to give the cycloadducts in high optical purity [43]. The boryl group was converted to an hydroxyl group stereospecifically by oxidation, and the alcohol obtained was used as the key intermediate in a total synthesis of (-i-)-paniculide A [44] (Scheme 1.56). 

Wefero-Dlels-Alder reactions of 3,5-di-fe/-f-butyl-o-benzoquinone with acyclic dienes novel synthesis of 1,4-benzodioxanes [135]... 

The transformation of conjugated dienes to allylsilanes can also be carried out with asymmetric induction. The efficiency of the asymmetric synthesis for acyclic dienes is moderate, but for cyclic dienes it remains to be improved. Nevertheless, these reactions provide us with a method for the preparation... 

Reaction of CoBr(PMe2)3 with acyclic dienes (butadiene, isoprene) yields square pyramidal [(n -diene)Co(PMe2)2] cations. Details of the application in organic synthesis of the CpCo(C0)2... 

Acyclic dienes react with glyoxylic acid via an oxo-Diels-Alder reaction to give dihydropyran derivatives (Eq. 12.53). An excellent application of the oxo-Diels-Alder reaction is reported by Lubineau et al. in the synthesis of the sialic acids, 3-deoxy-Z)-manno-2-octulosonic acid (KDO) and 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN).123... 

It has been established that the course of the sequential pericyclic reaction of cyclopentadienones with acyclic conjugated alkadienes depends on the reaction temperature, thermal treatment at low temperatures affording 3a,4,7,7a-tetrahydroinden-l-one derivatives by way of a Cope rearrangement (see Scheme 38). Roman et al have developed an efficient stereoselective synthesis of enantiomerically pure i-nitrotricyclo[5.2.2.0 ]undeca-3,8-dienes via a tandem consecutive asymmetric Diels-Alder-Cope rearrangement (see Scheme 39). Adducts... 

The initial work on the asymmetric [4-1-2] cycloaddition reactions of A -sulfinyl compounds and dienes was performed with chiral titanium catalysts, but low ee s were observed <2002TA2407, 2001TA2937, 2000TL3743>. A great improvement in the enantioselectivity for the reaction of AT-sulfinyl dienophiles 249 or 250 and acyclic diene 251 or 1,3-cyclohexadiene 252 was observed in the processes involving catalysis with Cu(ll) and Zn(ii) complexes of Evans bis(oxazolidinone) (BOX) ligands 253 and 254 <2004JOC7198> (Scheme 34). While the preparation of enantio-merically enriched hetero-Diels-Alder adduct 255 requires a stoichometric amount of chiral Lewis acid complex, a catalytic asymmetric synthesis of 44 is achieved upon the addition of TMSOTf. 

A useful synthesis of benzo[c]furans, based on experiments described by Ried, has been published by White et It consists of the Diels-Alder reaction of an acyclic diene with dibenzoylacetylene (146) and subsequent ring closure of the resulting 1,2-diaroylcyclohexadiene with /j-toluenesulfonic acid in benzene there has, however, been one report where this... 

Diels-Alder cyclizations are thermal reactions, and recent significant developments in the use of microwave irradiation to pyridine synthesis have been reported, including a series of pyrazolo[3,4- ]pyridines from nitroalkenes and pyrazolylimines with reaction times of 5-10min (Equation 115) <2000T1569>. This method appears to be general to this bicyclic class for example, replacement of the substituent on the imine allows for a C-2-unsubstituted pyridine. A range of cyclic and acyclic dienes have also been reported. 

The latest paper in this field [83] concerns the synthesis of the (S,S)-l,l-bis-ethoxycarbonyl-2,2-bis-p-tolylsulfinylethene (83) and its dienophilic behavior. Reactions with cyclopentadiene occur neither under thermal conditions nor in the presence of Lewis acids, but required the use of high pressure (13 kbar) to afford an 87 13 mixture of 84a and 84b adducts. With acyclic 1-substituted dienes, the combined use of ZnBr2 catalysis and high pressures was required to achieve high yields of cyclohexadienes 84c, resulting from spontaneous pyrolytic desulfinylation of the adducts (Scheme 44). The optical purity of these cyclohexadienes (ee >97%) revealed that both the regioselectivity and diastereo-selectivity of these reactions are complete. 

Title Synthesis of A,B-Alternating Copolymers by Olefin Metathesis Reactions of Cyclic Olefins or Olefinic Polymers with an Acyclic Diene... 

Highly enantioselective alkylations a to acyclic diene complexes have been developed. Deprotonation of (91) with LDA to form an ester enolate, followed by reaction with iodomethane, gives the alkylated prodnct (92) in excellent yield with 82% ee (Scheme 153). Stereospecific remote alkylation was used in a synthesis toward macrolactin A (Scheme 154). In the synthetic seqnence, the primary... 

Olefin metathesis (OM) has proven to be one of the most important advances in catalysis in recent years based on the application of this chemistry to the synthesis of polymers and biologically relevant molecules [1-10]. This unique transformation promotes chain and condensation polymerizations, namely ring opening metathesis polymerization and acyclic diene metathesis polymerization (ADMET). Applications of metathesis polymerization span many aspects of materials synthesis from cell-adhesion materials [11] to the synthesis of linear polyethylene with precisely spaced branches [12]. 

Acyclic dienes bearing Oppolzer s sultam auxiliary 261 have been utilized in the synthesis of functionalized 1,4-dihydronaphthalenes <05JA15028>. Cycloaddition of dienes 261 with benzynes, generated from 2(trimethylsilyl)phenyl triflate 263 using cesium fluoride, provides cycloadducts 263 with excellent diastereoselectivities. 

Cyclic exo-methylene compounds bearing a chiral acetal function prove to be excellent dieno-philes in the noncatalyzed Diels-Alder reaction. Dioxolanones 8 react with cyclopentadiene (9) and acyclic dienes 12 and 15 to afford adducts with diastereoselectivities as high as 100% 28,29. The major adduct 16 from the addition of 8b to diene 15 has been applied to the synthesis of the top half of kijanolide30. 

Synthesis. - Cycloadditions. The azadiene (26) behaves as a dienophile with cyclopentadiene but as a diene with acyclic 1,3-dienes and with cyclohexa-... 

Not surprisingly, Martin s sulfurane mediates the production of acyclic dienes from allylic and homoallylic alcohols. In Heathcock s synthesis of altohyrtin C, secondary homoallylic alcohol 55 reacted with sulfurane 1 to yield the desired ( T)-alkene 56 in greater than 84% yield.26 Interestingly, Tse generated diene 58 from tertiary allylic alcohol 57 in 95% yield with only 5% of the undesired trisubstituted diene isomer.27... 

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