Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

To dienes

Later m this chapter we 11 see how allylic carbocations are involved m elec trophihc addition to dienes and how the principles developed m this section apply there as well... [Pg.394]

Addition of HCN to unsaturated compounds is often the easiest and most economical method of making organonitnles. An early synthesis of acrylonitrile involved the addition of HCN to acetylene. The addition of HCN to aldehydes and ketones is readily accompHshed with simple base catalysis, as is the addition of HCN to activated olefins (Michael addition). However, the addition of HCN to unactivated olefins and the regioselective addition to dienes is best accompHshed with a transition-metal catalyst, as illustrated by DuPont s adiponitrile process (6—9). [Pg.217]

Vinylboranes are interesting dienophiles in the Diels-Alder reaction. Alkenylboronic esters show moderate reactivity and give mixtures of exo and endo adducts with cyclopentadiene and 1,3-cyclohexadiene (441). Dichloroalkenylboranes are more reactive and dialkylalkenylboranes react even at room temperature (442—444). Dialkylalkenylboranes are omniphilic dienophiles insensitive to diene substitution (444). In situ formation of vinyl-boranes by transmetaHation of bromodialkylboranes with vinyl tri alkyl tin compounds makes possible a one-pot reaction, avoiding isolation of the intermediate vinylboranes (443). Other cycloadditions of alkenyl- and alkynylboranes are known (445). [Pg.321]

The addition of hydrogen halides to dienes can result in either 1,2- or 1,4-addition. The extra stability of the allylic cation formed by proton transfer to a diene makes the ion-... [Pg.356]

Certain 1,5 diazabicyclo[3 3 0]oct-2-enes can be transformed unexpectedly into 4//-5,5-dihydro-l, 2 diazepines on heating [209] 1,5-Dipoles formed on heating of l,5-diazabicyclo[3 3 0]oct-2-enes [210] can be trapped with olefins to give [3+2] cycloadducts At elevated temperatures, they undergo a [3+2] cycloreversion Tins reaction sequence offers a simple route to dienes with interesting substitution patterns, for example, 1,1 bis(trifluoromethyl)-l,3-butadiene [211] The [3+2] cycloadducts that arise from the reaction of the 1,5 dipoles with acetylenes undergo... [Pg.868]

The use of lead tetraacetate to carry out oxidative bisdecarboxylation of diacids has been found to be a highly useful procedure when used in conjunction with the Diels-Alder addition of maleic anhydride to dienes, the latter process providing a ready source of 1,2-dicarboxylic acids. The general pattern is illustrated in the reaction... [Pg.14]

V. Bridged Sulfides by Addition of Sulfur Dichloride to Dienes... [Pg.57]

Regioselective addition of bromine azide to dienes 38 at 25 °C gave the 1,4-adducts 39 or the 1,2-adducts 40 as thermodynamically favored products, their ratios depending on the substituent R on the terminal carbon (Scheme 2.12). These adducts were easily converted into vinylaziridines 41 on treatment with trimethyl-phosphite, although the stereochemistries of 39, 40, and 41 are unclear [23]. [Pg.43]

Scheme 2.12 Synthesis of vinylaziridines through addition of bromine azide to dienes. Scheme 2.12 Synthesis of vinylaziridines through addition of bromine azide to dienes.
The above stereoselective additions of SO to dienes could have been predicted from its ground triplet state. [Pg.425]

While (Z)-l,2-bis(phenylsulfonyl)ethylene (140) does not add to dienes such as furan, cyclopentadiene, cyclo-octatetraene, indene and /f-naphthol, ( )-l,2-bis(phenylsulfonyl)ethylene (141) is more reactive and the reaction with furan proceeds at room temperature for 2 h to give the adduct in 95% yield. The reactivity of dienophiles having sulfonyl group in the [4 + 2]cycloaddition is shown in equation 10393,101. [Pg.791]

The substituents at C-2, C-3 within diene 97 and those at C-1, C-2 within dienophiles 98-100 are electronically and/or sterically equivalent with respect to diene and dienophile reaction centers, respectively, and therefore cycloaddition should not display regiochemical bias in the absence of orientational effects. The Diels-Alder reactions of 97 prepared in situ with 98-100 gave an excess of 101 (Scheme 4.19) [70b], which are the expected regioisomers if the reagents react in their preferred orientations within a mixed micelle with an ammonium head group at the aggregate-water interface and the remainder in the micelle interior. [Pg.175]

Diels-Alder reaction of the furan derivative 148 with homochiral bicyclic enone 149 is the key step [56] in the total synthesis of the diterpenes jatropho-lone A and B, 151 and 152, respectively, isolated from Jatropha gossypiifolia L [57], Initial efforts to carry out the cycloaddition between 148 and 149 under thermal or Lewis-acid conditions failed due to diene instability. Application of 5kbar of pressure to a neat 1 1 mixture of diene and dienophile afforded crystalline 150 with the desired regiochemistry (Scheme 5.23). Subsequent aromatization, introduction of the methylene group, oxidation and methylation afforded (-l-)-jatropholones 151 and 152. [Pg.232]

Additions of Kolbe radicals to dienes are reported in refs. [45, 215, 228] and in the reviews named in chap. 1. [Pg.111]

Silanes (R3SiH) also add to alkenes to form a new alkyl silane (RaSi—R ) in the presence of a hyponitrite. Silanes add to dienes with a palladium catalyst, and asymmetric induction is achieved by using a binapthyl additive. ° ... [Pg.1018]

Simpler bicyclobutanes can also be converted to dienes, but in this case the products usually result from cleavage of the central bond and one of the edge... [Pg.1460]

Addition of unsaturated boranes to methyl vinyl ketones Hydrocarboxylation of triple bonds Addition of acyl halides to triple bonds 1,4-Addition of acetals to dienes... [Pg.1691]

During the past decade, many papers have dealt with the facial selectivities of Diels-Alder reactions, particularly in relation to dienes [153-159], and various attempts have been made to rationalize the origins of the selectivities [160]. The facial selectivities of Diels-Alder reactions are discussed in detail in Chapter jt-Fadal Selectivity of Diels-Alder Reactions by Ishida and hiagaki in this volume. In this and the following section, we will consider the facial selectivities of Diels-Alder reactions in terms of orbital phase enviromnent. [Pg.161]


See other pages where To dienes is mentioned: [Pg.361]    [Pg.407]    [Pg.407]    [Pg.182]    [Pg.438]    [Pg.572]    [Pg.844]    [Pg.407]    [Pg.407]    [Pg.57]    [Pg.38]    [Pg.400]    [Pg.792]    [Pg.296]    [Pg.348]    [Pg.141]    [Pg.1646]    [Pg.1649]    [Pg.1672]   
See also in sourсe #XX -- [ Pg.978 ]




SEARCH



A,to-Diene

A.to-Dienes

Addition of Active C-H compounds to Dienes the Rhone-Poulenc Process for Geranylacetone

Addition of Amines to Conjugated Dienes

Addition of Hydrogen Halides to Conjugated Dienes

Addition reactions to conjugated dienes

Addition reactions to dienes

Addition to 1,3-Dienes and 1,3-Dipoles

Addition to a Conjugated Diene

Addition to dienes

Alkyne To diene

Apparent 1,4 Addition to Dienes

Azines cycloaddition to 1,3-dienes

Bridged Sulfides by Addition of Sulfur Dichloride to Dienes

Chlorine to conjugated dienes

Cycloaddition to 1,3-Diene

Cycloaddition to Conjugated Dienes The Diels-Alder Reaction

Cycloaddition to conjugated dienes

Cycloaddition to dienes

Cyclobutenes photochemical ring-opening to dienes

Cyclobutenes ring-opening to dienes

Electrophilic Additions to Conjugated Dienes Allylic Carbocations

Electrophilic Additions to Conjugated Dienes Allylic arbocations

Electrophilic addition to conjugated dienes

Electrophilic addition to dienes

Elimination to Form Conjugated Dienes

Halogen Addition to Dienes

Hydrogen bromide to conjugated dienes

Hydrogen chloride to conjugated dienes

Hydrogen halides to conjugated dienes

Hydrogenation of dienes to monoenes

Kinetic control to conjugated dienes

Nucleophilic additions to 1,3-dienes the synthesis of geranylacetone

Palladium-catalyzed 1,4-additions to conjugated dienes

Radical Addition to Alkenes, Dienes, and Polyenes

Radical addition of HBr to conjugated dienes

Sulfur dichloride Diels-Alder additions to dienes

Thermodynamic control addition to dienes

Use of RLi to Prepare Terminally Functional Diene (Olefin) Polymers

© 2024 chempedia.info