Ene synthesis

Derivatives of polyisobutylene (6. in Figure 9.1) offer the advantage of control over the molecular weight of the polyisobutylene obtained by cationic polymerization of isobutylene. Condensation on maleic anhydride can be done directly either by thermal activation ( ene-synthesis reaction) (2.1), or by chlorinated polyisobutylene intermediates (2.2). The condensation of the PIBSA on polyethylene polyamines leads to succinimides. Note that one can obtain mono- or disuccinimides. The mono-succinimides are used as... 

Azabicyclo[2.2.0]hexa-1,3,5-triene reactions, 7, 360 2-Azabicyclo[2.2.0]hex-5-ene reactivity, 7, 342 synthesis, 2, 371 2-Azabi cyclop. 1.0]hexene synthesis, 2, 371 2-Azabi cyclop. 1.0]hex-2-ene synthesis, 7, 67 2-Azabicyclo[k 1.0]hex-3-ene synthesis, 4, 258 6-Azabicyclo[k 1.0]hex-2-ene synthesis, 2, 305 Azabi cyclohexenes formation from azirines, 7, 58... 

Thiabicyclo[3.1.0]hex-3-ene synthesis, 4, 784 9-Thiabicyclo[3.3.1]nonane 9,9-dioxide bond angles, 7, 409 5-Thiabicyclo-2-pentene, 1,2,3,4-tetrakis(trifiuoromethyl)-rearrangement, 7, 153 2H-l,2-Thiaborin dibenzo fused, 1, 658 1-Thia[2.2.2]cyclazines, 4, 479 5-Thia[2.3.3]cyclazines, 4, 481 Thiacyclobutadienes — see lH-1 A -Thietes... 

Alkenes can add to double bonds in a reaction different from those discussed in 15-19, which, however, is still formally the addition of RH to a double bond. This is called the ene reaction or the ene synthesis For the reaction to proceed without a catalyst, one of the components must be a reactive dienophile (see 15-58 for a definition of this word) such as maleic anhydride, but the other (which supplies the hydrogen) may be a simple alkene such as propene. Cyclopropene has also been used. ° The reaction is compatible with a variety of functional groups that can be appended to the ene and dienophile. N,N-Diallyl amides give an ene cyclization. 

Note that a [ 1,5] sigmatropic rearrangement of hydrogen is also an internal ene synthesis (15-20). 

The step marked A is similar to the ene synthesis (5-16). The step marked B is a [2,3] sigmatropic rearrangement (see 8-37). The reaction can also be accomplished with... 

Several mechanisms have been proposed for the reaction with singlet oxygen.221 One of these is a pericyclic mechanism, similar to that of the ene synthesis (5-16) and to the first... 

This reaction is reversible and suitable p-hydroxy olefins can be cleaved by heat (7-43). There is evidence that the cleavage reaction occurs by a cyclic mechanism (p. 1043), and, by the principle of microscopic reversibility, the addition mechanism should be cyclic too.719 Note that this reaction is an oxygen analog of the ene synthesis (5-16). This reaction can also be done with unactivated aldehydes7211 and ketones721 if Lewis-acid catalysts such as... 

Reactions described in this chapter that are catalyzed by mixed-function oxidases are those involved in fatty acyl-CoA desaturation (Fig. 21-13), leukotri-ene synthesis (Fig. 21-16), plasmalogen synthesis (Fig. 21-30), conversion of squalene to cholesterol (Fig. 21-37), and steroid hormone synthesis (Fig. 21-47). 

Silacyclopentan-2-ol properties, 1, 612 Silacyclopentan-3-ol properties, 1, 612 Silacyclopent-3-ene, 1,1 -dichloro-NMR, 1, 614 Silacyclopentenes flash vacuum pyrolysis, 1, 615 synthesis, 1, 610-612 Silacyclopent-2-enes synthesis, 1, 610 Silacyclopent-3-enes properties, 1, 612 reactions... 

Stannacyclopentane, 1,1-dimethylring opening, 1, 608 Stannacyclopentanes, 1, 605-609 chemical properties, 1, 607-608 insertion reactions by sulfodiimides, 1, 608 ring opening, 1, 608 synthesis, 1, 605-607 Stannacyclopent-3-enes synthesis, 1, 616 Stannacyclopropanes synthesis, 1, 581 Stannaindanes formation, 1, 581 7-Stannanorbornadiene decomposition, 1, 619 Stannin, dihydroreplacement of tin with arsenic, antimony or bismuth, 1, 553 Stannoles... 

Bis(aryloxo) complexes, with mono-Cp Ti(IV), 4, 474 Bis(aiyloxo) titanacyclopent-2-ene, synthesis, 4, 358 Bis(A7-azain do Mi methane-coordinated complexes, with platinum(II), 8, 475... 

The maleimide C=C double bond can undergo a Diels-Alder reaction with dienes for example, reaction with o,o -diallylphenols is thought to proceed initially by ene-synthesis, followed by Diels-Alder reaction ... 

The reaction of a BMI with an acetylenic end-capped oligomer has been undertaken. The mechanism was thought to proceed according to the two pathways indicated in Fig. 21 either by a kind of ene synthesis with formation of an hypothetic cycloallene leading to a dihydronaphthalene derivative (pathway a) or by a condensation concerted with an hydride shift (pathway b). No experimental proof was given for the structure but the condensation of both oligomers gave an expected linear product with a better Glc than the one of BMI alone (324 J m 2 vs. 34 J m 2) [73]. 

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