Enynes skeletal reorganization

Platinum complexes (continued) with aryls, thallium adducts, 3, 399 with bis(alkynyl), NLO properties, 12, 125 with bisalkynyl copper complexes, 2, 182-186 with bis(3,5-dichloro-2,4,6-trifluorophenyl), 8, 483 and C-F bond activation, 1, 743 in C-H bond alkenylations, 10, 225 in C-H bond electrophilic activation studies, 1, 707 with chromium, 5, 312 with copper, 2, 168 cyclometallated, for OLEDs, 12, 145 in diyne carbometallations, 10, 351-352 in ene-yne metathesis, 11, 273 in enyne skeletal reorganization, 11, 289 heteronuclear Pt isocyanides, 8, 431 inside metallodendrimers, 12, 400 kinetic studies, 1, 531 on metallodendrimer surfaces, 12, 391 mononuclear Pt(II) isocyanides, 8, 428 mononuclear Pt(0) isocyanides, 8, 424 overview, 8, 405-444 d -cP oxidative addition, PHIP, 1, 436 polynuclear Pt isocyanides, 8, 431 polynuclear Pt(0) isocyanides, 8, 425 Pt(I) isocyanides, 8, 425 Pt(IV) isocyanides, 8, 430... 

Enyne metathesis is unique and interesting in synthetic organic chemistry. Since it is difficult to control intermolecular enyne metathesis, this reaction is used as intramolecular enyne metathesis. There are two types of enyne metathesis one is caused by [2+2] cycloaddition of a multiple bond and transition metal carbene complex, and the other is an oxidative cyclization reaction caused by low-valent transition metals. In these cases, the alkyli-dene part migrates from alkene to alkyne carbon. Thus, this reaction is called an alkylidene migration reaction or a skeletal reorganization reaction. Many cyclized products having a diene moiety were obtained using intramolecular enyne metathesis. Very recently, intermolecular enyne metathesis has been developed between alkyne and ethylene as novel diene synthesis. 

Trost and Tanoury found an interesting skeletal reorganization of enynes using a palladium catalyst.In this reaction, the second product is derived from a metathesis reaction (Equation (5)). It was speculated that the reaction would proceed by oxidative cyclization of enynes with the palladium complex followed by reductive elimination and then ring opening. To confirm this reaction mechanism, they obtained a compound having a cyclobutene ring, which was considered to be formed by the reductive elimination (Equation (6)). 

PtCl2 constitutes an efficient and practical catalyst for skeletal rearrangement reaction of enynes. This includes a formal enyne metathesis reaction delivering 1,3-dienes. Skeletal reorganization of enyne 75a having a carbon chain in... 

Iridium complex [IrCKCOls] also catalyzes skeletal reorganization of enyne 78d to 79d (Scheme 32). In contrast, enyne 78e having a methyl group on an alkyne terminal fails to give any products under the same reaction. Use of... 

Very recently, the same group reported skeletal reorganization of enynes to 1-vinylcycloalkene by GaCls-Reaction of 78f, for example, proceeds in toluene at 0 °C and is completed within 1 h to give 79f. It is interesting that highly strained cyclobutene derivative 82 is obtained from 1,7-enyne 78g (Scheme 33). 

Trost succeeded in formal total synthesis of roseophilin. Macrocyclic compound 118 is synthesized from enyne 117 by platinum-catalyzed skeletal reorganization reaction and is converted into 119, which is further converted into pyrrole derivative 120 (Scheme 43). ... 

The addition of aryl halides and divinyl or enyne carbinols to give tri- or tetra-substituted alkenes is considered to involve skeletal reorganization (Scheme 89) of an intermediate cyclopropanol.132 The ability to suppress /3-hydride elimination of organopalladium intermediates is critical to the success of these processes. 

The term intramolecular enyne metathesis describes two types of processes. One involves a [2+2] cycloaddition of a multiple bond and a transition-metal carbene complex and the other is an oxidative cyclization catalyzed by low-valent transition-metal complexes, for example, Pt, Pd and Ru. The latter reaction is also called a skeletal reorganization. Both processes lead to similar products (Eq. 84). 

Ruthenium-catalyzed skeletal reorganization involving organosilicon compounds have been reported by Chatani et al. [ 140] (Eq. 85). The reaction provides an efficient method for converting enynes to vinylcycloalkenes. 

Transition metal-catalyzed carbocyclizations of 1,6-enynes A [7-11] such as cycloisomerization [12-18], metathesis [19-30], skeletal reorganization [31-34], and ene reactions [35] are useful synthetic methods leading to five-membered rings (Scheme 4). Transition metal-catalyzed carbocyclizations of... 

By use of Ru-based carbenes such as [Ru]-Ia, II, III, various carbo- and heterocycles can be synthesized from the corresponding enyne precursors. The metathesis is carried out not only by ring-closing enyne metathesis but also by dienyne metathesis, cross enyne metathesis, and ring-opening enyne metathesis.In this section, the synthetic applications of enyne metathesis reactions, including skeletal reorganization reactions and hetero-enyne metathesis, to natural products and related compounds are described. 

Skeletal reorganization of enynes also provides a straightforward procedure for the preparation of 1,3-diene compounds, in which there are two possible products, type I and II products. The generally accepted mechanism for the skeletal reorganization of enynes was illustrated in Scheme 24.66. Although the type I product is similar to diene generated by the Ru-carbene-catalyzed enyne RCM reaction, the product is considered to be formed through path a and/or path b by an electrophilic activation of a metal catalyst to alkynes. The formation of the type II... 

SCHEME 24.67. Transition-metal-catalyzed skeletal reorganization of enynes. 

Trost and Doherty applied the Pt-catalyzed skeletal reorganization reaction of enyne 281 to the construction of bicyclic compound 282 for the formal total synthesis of roseophilin 285, which was isolated from Streptomyces... 

Lee SI, Chatani N. Catalytic skeletal reorganization of enynes through electrophilic activation of alkynes double cleavage of C C double and triple bonds. Chem. Commun. 2009 371-384. 

Chatani N, Morimoto T, Muto T, Mural S. Highly selective skeletal reorganization of 1,6- and 1,7-enynes to 1-vinylcy-cloalkenes catalyzed by [RuCl2(CO)3]2. J. Am. Chem. Soc. 

Chatani N, Kataoka K, Mural S, Furukawa N, Seki Y. Con-stmction of novel polycyclic ring systems by transition-metal-catalyzed cycloisomerization of ene-ene-ynes. Interception of a carbenoid intermediate in skeletal reorganization of enynes. J. Am. Chem. Soc. 1998 120 9104-9105. 

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