Cyclization allylation reactions

Although yields for the reactions with monocyanonaphthalines could exceed 70%, 2,3-disubtituted-l,4-dicyanonaphthalines failed to cyclize after the initial allylation reaction [69]. 

Perfluoronaphthalene undergoes an intermolecular substitution followed by intramolecular cyclization on reaction with allyl bromide and mercaptide ion to furnish a dihydrothiophene denvative in high yield [34] (equation 23). 

The palladium-catalyzed cyclizative coupling reaction of a-allenols 41 with alkenyl halides was also explored. The transformation of allenols 41 into spirocyclic disubstituted dihydrofuran (3-lactams 43 was readily achieved in high yields, by treatment with allyl bromide or 2,3-dibromopropene in the presence of palladium (II) chloride (5 mol%) (Scheme 14) [60]. 

Tandem Radical 5-exo Cyclization/Heck Reactions or Tandem Radical Cyclization/Allylic Substitution Reactions... 

Me3SiCN is a convenient, reactive cyanide donor in transition metal-catalyzed processes. The Pd-catalyzed reaction of aryl iodides with Me3SiCN is useful for the synthesis of aryl cyanides.257 Me3SiCN works also as an effective co-catalyst for the Pd-catalyzed cyanation of aryl iodides with KCN.258 Allylic acetates, carbonates, and the related compounds undergo the Pd-catalyzed cyanation with Me3SiCN.259-261 The tandem cyclization-cyanation reaction of 2-bromo-l,6-heptadienes with Me3SiCN proceeds under catalysis by an Ni complex (Equation (68)).262... 

Several indium-mediated intramolecular carbonyl allylation reactions have been investigated, and it has been found that these reactions provide an easy access to a variety of cyclic compounds. The intramolecular cyclization of 49a-c mediated by indium in aqueous media proceeds smoothly to afford carbocyclic systems containing y-hydroxy-Q -methylene esters 50a-c, which either spontaneously or readily cyclize to give fused o -methylene-y-butyrolactones 51a-c (Scheme 52). The same cyclization of 49d is too slow to compete with the side-reaction, in which the bromide is substituted by a hydroxy group. The ring junction stereochemistry of fused lactones 51 has been found to be cis in all cases. Of the two possible transition states, the one leading to the m-fused compounds is preferred, because the chair-chair conformation is favored over the chair-boat conformation.209... 

In a similar way, 2-oxazolidinones and tetrahydro-2//-l, 3-oxazin-2-ones have been prepared by the reaction of primary allyl amines and homoallyl amines10, respectively, with carbon dioxide and iodine in methanol via an intramolecular cyclization. Prolonged reaction for a week in the presence of cesium carbonate increases the yield to 70-90%. This reaction has a large applicability and the ease of the method makes it useful in organic synthesis. 

The intramolecular version of this reaction has many applications. The stereochemistry of the starting material shown in Eq. (168) seems to influence the efficiency of the reaction [421,422]. The acceptor of the allylic cationic species is not limited to conjugated dienes. The following result shown in Eq. 169 indicates that a simple terminal olefin might serve as the reaction partner to give bicyclic cyclopentane skeleton [423]. In this formal [3 -n 2] cyclization, the reaction should proceed stepwise. Other results of inter- or intramolecular [3 -1- 4] or [3 -1- 2] cyclizations are collected in Table 15. The stereochemistry of the reactions has been studied in detail and is the subject of more extensive reviews [418,424]. 

Cyclization. Allyl o-iodoaryl ethers, A7,Al-diallyl-2-iodoaniline, and related compounds furnish dihydrobenzofuran and indoline products via radical intermediates on reaction with Bu,MnLi. 

The addition processes are characterized as Type II allylation reactions and featnre open transition states. Denmark and Keck have described mechanistic studies, which have provided basic information shaping current views regarding the Type II allylations of organostannanes. Denmark s models are briefly summarized by the cyclization of deuterium-labeled 4 (Scheme 5.2.2). Intra-molecular allylation proceeds with Lewis and Brpnsted acids to yield 6 with high selectivity. The alcohol 6 is rationalized throngh the synclinal transition state 5 via anti-Su substitution. To a lesser degree, various Lewis acids also produce the... 

In a related area, triarylphosphonium-supported tin reagents were very recently used for Stille crosscoupling reactions, dehalogenation reactions, cyclization reactions, and allylation reactions affording the desired products with very low tin pollution (5-15 ppm). ... 

Nickel and Grignard catalyzed stereoselective synthesis of cis and trans 2-alkyl-vinylcyclopentanes from telemerization of butadiene. Cyclization (ene reaction) of unsaturated allyl Grignard reagents, see also Feldman (see 1st edition). 

Reaction with a, -epoxy ketones. Swiss chemists have reported a case in which the Wharton reaction (1,, 439-440) led not only to the expected allylic alcohol but also to a product of cyclization. Stork and Williard have investigated this reaction in detail and have observed several more examples of the formation of cyclized allylic alcohols in the Wharton reaction as shown in the examples. On the other hand, several related systems were converted only into the products expected from a Wharton reaction. At the present time, the subtle factors that lead to cyclization are not well understood. 

The use of carbanionic nucleophiles in the Mizoroki-Heck cyclization-/ -allyl nucleophilic trapping sequence allowed for streamlined access to the triquinane core common to various members of the capnellene family of natural products. For example, Shibasaki and coworkers obtained diquinane 57 in 77% yield and 87% ee by Mizoroki-Heck cy-clization of trienyl triflate 47 in the presence of malonate nucleophile 56 Scheme 16.14). It is notable that two new C-C bonds and three stereocentres are generated in this reaction. Eleven additional steps were used to convert intermediate 57 to ( )-A ( Ecapnellene (58). This first catalytic asymmetric total synthesis ( )-A d2). j pjjgjjgjjg achieved in 19 steps and 20% overall yield from commercially available materials. A related approach has recently been employed to prepare intermediates en route to capnellenols 53 and 54 (Scheme 16.12) [41]. 

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