Methylenecyclopentane derivatives

The intramolecular carbopalladation (or insertion) of the triple bond in dimethyl 4-pentynylmalonate (215) with Pd—H species and malonate anion as shown by 216 proceeds in the presence of f-BuOK and 18-crown ether, affording the methylenecyclopentane derivatives 217 and 218, the amounts of which depend on the reaction conditions. The Pd—H species may be formed... 

The cycloadditions in entries 1-3 are still believed to occur via a diradical stepwise pathway, as confirmed by obtaining a thermodynamic 78 22 trans/cis mixture of dispirooctanes 536 from frans-dicyanoethylene (533) (entry 3) [13b, 143], The cycloaddition to tetracyanoethylene (131) in the absence of oxygen gives only low yields of the [2 + 2] adduct, due to the simultaneous formation of products 542 and 543 (Scheme 74) [13b]. Still, the formation of the cyclobutanes 537 and 542 is noteworthy, since the reactions of TCNE with phenyl substituted MCPs exclusively afford methylenecyclopentane derivatives [37,144], The reaction is thought to occur via dipolar intermediates 539-541 formed after an initial SET process (Scheme 74) [13b]. The occurrence of intermediates 540 and 541 has been confirmed by trapping experiments [13b]. 

The diester 226 undergoes ring-closure to the methylenecyclopentane derivative 227 in the presence of a catalytic amount of chlorotris(triphenylphosphine)rhodium in boiling chloroform saturated with hydrogen chloride. In contrast, if the reaction is catalysed by palladium(II) acetate, the isomeric cyclopentene 228 is produced (equation 115)118. 

Two molecules of norbornene 116 are incorporated in its coupling with / -bromostyrene to yield the bisnorbornane-annelated methylenecyclopentane derivative 120. But under different conditions, the reaction proceeds with the reverse 2 1 stoichiometry to give the cyclohexadiene-annelated norbornane derivative 121 (Scheme 32). ... 

Nickel catalyzed [3 + 2] cycloadditions of methylenecyclo-propane and 2,2-dimethylmethylenecyclopropane with (4) afford 3-methylenecyclopentane derivatives with extremely high TT-face selectivities (91% and 98% de respectively) five alternative auxiliaries were found to be less effective. - Palladium catalyzed [3 + 2] cycloaddition of 2-(TMS-methyl)-3-acetoxy-l-propene with an N-enoylsultam, however, proceeds with disap-... 

An interesting intramolecular variation of this reaction provides oxazolidones, which may be hydrolyzed to synthetically useful optically active 2-amino-3-butenols (eq 8). The absolute stereochemistry of the stereocenter formed is dependent upon the geometry about the double bond of the 2-butenylene dicarbamate substrate. A related Pd -promoted [3 + 2] cycloaddition of an activated alkene with a 2-(sulfonylmethyl)-2-propenyl carbonate, using the bis(hydroxyalkyl)-substituted ligand (8), gave methylenecyclopentane derivatives with high asymmetric induction. ... 

Asymmetric [3 + 2] cycloaddition of 2-(sulfonylmethyl)-2-propenyl carbonate 56 with methyl acrylate or methyl vinyl ketone is also catalyzed by the palladium-ferrocenylphosphine 8b complex to produce methylenecyclopentane derivatives with up to 78% ee (Scheme 2-36) [52]. 

A thia-Wittig rearrangement in the methylenecyclopentane (154) proceeded to (155) without formation of the epimer (equation 45). Obviously, the reaction proceeds on the less hindered (convex) face of the bicyclic framework. Equally high diastereoselectivity — unassigned, but presumably also on the less hindered (exo) face — is recorded for the 2,3-rearrangement of a methylenecyclopentane-derived sulfur ylide. ... 

Cyclopolymerization of 2-methyl-l,5-hexadiene is catalyzed by a cationic zir-conocene complex [75]. Isolation of methylenecyclopentane derivatives 55-57 from the low molecular weight oligomeric products provides convincing evidence for chain transfer via P-methyl elimination. 

Triorganylphosphane-modified palladium(O) compounds catalyze the codimerization of methylenecyclopropane with ethene, norbornene, dicyclopentadiene or norbomadiene to give substituted methylenecyclopentane derivatives. Here, in all cases, the three-membered ring is opened between C2 and C3. " ... 

Cycloaddition.2 In the presence of this nickel catalyst, methylenecyclo-propanes undergo an unusual cycloaddition across carbon-carbon double bonds. Thus methylenecyclopropane (1) when heated in a sealed tube (60°, 48 hrs.) with excess methyl acrylate in the presence of bis(acrylonitrile)nickel(0) gives the 1 1 adduct, methyl 3-methylenecyclopentanecarboxylate (2), in 82% yield. Methyl vinyl ketone or acrylonitrile is also a suitable substrate. The reaction provides a useful synthesis of methylenecyclopentane derivatives. 

Acetoxymethyl)-3-(trimethylsilyl)propene (1) is used as a trimethylenemethane precursor in palladium(0)-catalvzed [3 + 2] cycloaddition with electron-deficient alkenes, such as enones, acrylonitriles and a,/ -unsaturaled esters23,26. Mechanistically, this reaction, which gives methylenecyclopentane derivatives 2. is interpreted to proceed via trimethylenemethane-palladium complexes 27,28. 

Cycloisomerization. The photoinduced formation of methylenecyclopentane derivatives from a-(4-pentynyl)acetoacetic esters represents a new way to prepare these substances. 

Intramolecular termination by carbon nucleophiles has been achieved with dialkyl malonate moieties. These cascade reactions, developed essentially by Balme, Gore, and colleagues, open an avenue especially to variously substituted methylenecyclopentane derivatives (Scheme 19,and Sect. V.3.4). 

Hydrocarbocyclization reactions of various active methine compounds having an unactivated 4-alkynyl or allenyl group, to form methylenecyclopentane derivatives in good yields, have been promoted catalytically by NaH or n-BuLi without the assistance of a transition metal. ... 

Trimethylsilylmethyl)allyl aeetate (80), whieh has a silyl group in the allylic position undergoes a formal [3 + 2] eyeloaddition reaction with electron deficient alkenes to give methylenecyclopentane derivatives 84. Following oxidative addition, elimination of the TMS group, faeilitated by... 

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