Cycloaddition of allene with

The 1,3-dipolar cycloaddition of allenes with 1,3-dipoles has been reviewed.56 The scope and limitations of palladium-catalysed intramolecular 3 + 2-cycloaddition of diastereomerically pure methylenecyclopropanes (33) yielding methylenecyclopentenes (34) has been investigated (Scheme 12).57 Chiral 2,5-dialkyl-7-phenyl-7-phosphabicy-... 

SCS-MP2 and the new perturbative B2-PLYP density functional methods provide accurate reaction barriers and outperform MP2 and B3-LYP methods when applied to the 1,3-dipolar cycloaddition reactions of ethylene and acetylene.39 Phosphepine has been shown to catalyse the asymmetric 3 + 2-cycloaddition of allenes with a variety of enones (e.g. chalcones) to produce highly functionalized cyclopentenes with good enantiomeric excess.40 The AuPPh3SbF6 complex catalysed the intramolecular 3 + 2- cycloaddition of unactivated arenyne- (or enyne)-yne functionalities under ambient conditions.41 A review of the use of Rh(I)-catalysed 3 + 2-cycloadditions of diaryl-and arylalkyl-cyclopropenones and aryl-, heteroaryl-, and dialkyl-substituted alkynes to synthesise cyclopentadienones for use in the synthesis of natural products, polymers, dendrimers, and antigen-presenting scaffolds has been presented.42... 

Wilson, J.E. and Fu, G.C. (2006) Synthesis of functionalized cyclopentenes through catalytic asymmetric [3 + 2] cycloadditions of allenes with enones. Angewandte Chemie, International Edition, 45, 1426-1429. 

The first step is a photochemical [2+2] cycloaddition. You could not have predicted the regio-chemistry, but it is typical of the cycloaddition of allenes with unsaturated ketones. 

In 1984, Schreiber published a synthesis of the pheromone in which the majority of steps involve pericyclic reactions. Make sure you understand each one as it appears—re-read the appropriate part of Chapter 34 or this chapter if you have any problems. The first step is a photochemical [2 + 2] cycloaddition. You could not have predicted the regiochemistry, but it is typical of the cycloaddition of allenes with unsaturated ketones. 

Scheme 6.19 [3 -E 2] Cycloadditions of allenes with iV-phosphinoyl imines.

Phosphine-Catalyzed Reactions Enantioselective [3+2] cycloaddition of allenes with enones leads to the synthesis of cyclopentenes, which can be further transformed to cyclopentanes (Scheme 6.4). The phosphine addition to allenoate generates an allylic carbanion, which undergoes addition to the enone in the a and the p positions followed by the phosphine elimination to afford 3 and 4, respeetively [6]. 

Scheme 8.23 Chirality transfer in Cr(0)-mediated [6-1-2] cycloaddition of allenes with cyclo-heptatriene under photochemical activation.

Furthermore, 12 was found to catalyze [3+2] cycloaddition of allenes with various -substituted a,P-unsaturated ketones to produce enantiomerically enriched, highly functionalized cydopentenes possessing two contiguous stereocenters [41], Along with this line, Marinetti reported that 2-aryl-l,l-dicyanoethylenes were also good reaction partners of the allenoates in the 12-catalyzed cydoaddition [42] (Scheme 7.24). 

Zhang B, He Z, Xu S, Wu G, He Z (2008) Nucleophilic phosphine-catalyzed [3 -I- 2] cycloaddition of allenes with JV-(thio)phosphoryl imines and acidic methanolysis of adducts iV-(thio)phosphoryl 3-pyrrolines a facile synthesis of free amine 3-pyrrolines. Tetrahedron 64 9471-9479... 

Cycloaddition of norbornadiene with allene takes place to yield the cyclobutene derivative 10[5], Cyclodimerization of 1,2-cyclononadiene (11) affords a mixture of stereoisomers of the cyclobutane derivatives 12[6,7],... 

Application in organic synthesis of optically active isoxazolidones obtained by asymmetric cycloaddition of nitrones with allenes 97T403. 

Electron-deficient olefins such as acrylonitrile can participate in the cross [2 + 21-cycloaddition with allenes. 3-Methylenecydobutanecarbonitrile (17) was obtained in 60% yield by the reaction of allene with a large excess of acrylonitrile under autogenous pressure at 200 °C [16]. Initial bond formation takes place between the central carbon of allene and the terminal carbon of acrylonitrile to give a diradical species, which cydizes to form the cydoadduct [17]. 

Intramolecular [2 + 2]-cycloadditions of allenes and enones occur with fair to good site- and regioselectivities. Thus, cyclohexenone 40 bearing an allenic side-chain at the C3 position was irradiated and a single product 41 was isolated in 95% yield [45],... 

The [3 + 2]-cycloaddition reactions of allenes with 1,3-dipoles are useful for the construction of a variety of five-membered heterocycles with a high degree of regio- and stereochemical control [67]. Generally, the dipolar cycloaddition reactions are concerted and synchronous processes with a relatively early transition state. The stereoselectivities and regiochemistries are accounted for by the FMO theory The reaction pathway is favored when maximal HOMO-LUMO overlap is achieved. 

The cycloaddition of allenic lactone 124 with cyclopentadiene was carried out under thermal conditions and also in the presence of a Lewis add catalyst [102]. In both cases, the exo-adduct was formed predominantly. 

The cycloaddition of allenes carrying an electron-withdrawing phosphorus substituent has also been studied [118]. Allenyl phosphine oxide 138 is prepared in a manner analogous to allenyl sulfoxide. The [4+ 2]-cycloaddition reaction of 138 with cyclopentadiene proceeded with a high endo selectivity. 

The most recent review54 about [2 + 2] cycloadditions of allenes covers the literature up to 1992. This section deals with recent results combined with some representative results from the past decade. 

The intramolecular 2 - - 2 - - 1-cycloadditions of allene, alkyne (106), and carbon monoxide yield a -methylene-(107) or 4-alkylidene-cyclopentenones (108) depending on the allene structure or the reaction conditions (Scheme 4i).i59.i6o The cobalt-catalysed 4 - - 2 - - 2-cycloaddition of norbornadienes (109) with buta-1,3-dienes readily produces cycloadducts (110) when a bimetal system is used (Scheme A2) ... 

The practical value of this type of reaction is restricted to symmetrical allenes with vastly different reactivities. Since the less reactive allene has to be present in excess or otherwise homodimerization competes, this allene has to be readily available in large quantities. An example of such a mixed dimerization is the cycloaddition of allene (2) with cyclonona-l,2-di-ene (1). ... 

The cycloaddition of allenes to symmetrically disubstituted alkenes gives mixtures of cyclobutanes with stereochemical equilibration of the substituents. The reaction of 1,3-dimethylallenc with either diethyl fumarate or diethyl maleate produces a mixture of the /raw.v-bis(ethoxycar-bonyl)cyclobutanes.s The same nonstereoselectivity was observed for phenylallene and 1,1-dimelhylallene cycloadditions to maleic and fumaric acid diesters.9 10... 

An ab initio study of the 2 + 2-cycloadditions of allene to isocyanic acid and ketene to vinylimine found the reactions to be concerted and mostly asynchronous.28,29 The diastereoselective 2 + 2-cycloaddition of dichloroketene with a chiral enol ether (26) produced the cyclobutanone (27), which leads to a key intermediate (28) in (g) the total synthesis of the natural alkaloid (-)-Swainsonine (29) (Scheme 8).30 The... 

Photocycloadditions with Cumulated Double Bonds. Wiesner discovered that the regioselectivity in intermolecular cycloadditions of allene to Q, 3-unsaturated ketones 8.50 gave the cyclobutane 8.51 with the central carbon of the allene bonded to the a position. The addition also took place with high stereoselectivity for attack on the lower face of the double bond in 8.50, surprisingly, because the lower face is the more hindered. The approach... 

Au(I) " or Pt(II) catalysts. Dienynes react with cationic Au(I) catalysts leading to products of formal [4 - - 2] cycloaddition as well (equation 65). " Somewhat related cyclizations of allenes with alkynes and diynes have been described. 

Lewis acid catalyzed reactions of allenes with alkenes generally give cyclobutanes rather than ene adducts. AlCb catalyzed reactions of alkylallenes with alkenes give alkylidenecyclobutanes. Similarly, AICI3 catalyzed reactions of alkynes with alkenes give cyclobutenes. These reactions are believed to occur by stereospecific cycloaddition of the alkene with the vinyl cation formed by complexation of AICI3 to the allene or alkyne. 

The cycloaddition reactions of allenes with trimethylsilyloxybutadienes produce phenols in good yield by regioselective cyclization and subsequent aromatization by acid-catalysed enolization (equation 116) ", or by fluoride-induced cleavage of the trimethylsilyl groups... 

---