2-Aryl- 1-methylenecyclopropane

The polymer structure is quite similar to those prepared from 2-aryl-1-methylenecyclopropanes with the Ni catalyst. The glass transition temperature is lower than that of the polymer with aryl substituents. 

Kim S, Takeuchi D, Osakada K (2003) Pd complex-catalyzed ring-opening polymerisation of 2-aryl- 1-methylenecyclopropanes. In Screttas CG, Steele BR (eds) Perspectives in organometallic chemistry. The Royal Society of Chemistry, Cambridge, p 306... 

The best method for the preparation of ring-alkylated and -arylated methylenecyclopropanes proves to be the dehydrochlorination of 1-chloro-l-methylcycloprop-anes (Route b). The latter are easily obtained from alkenes and 1,1-dichloroethane in the presence of a unable base6) (Eq. 52). 

Aryl-substituted methylenecyclopropanes 132 can undergo intramolecular cycloisomerisation in catalytic presence of NHC-Pd complex 133 to form 1,2-dihydronaphthalenes 134 in moderate yields (Scheme 5.35) [40],... 

R = H, Me, MeO, PrO, MegN, Cl, F Scheme 5.35 NHC-Pd catalysed cycloisomerisation of aryl-substituted methylenecyclopropanes... 

Interestingly, chloropalladation reaction of the more constrained cu-7-methylenebicy-clo[4.1.0]heptane did not afford the expected dis-in kinetic product but rather the rearranged to >/ to rf ) thermodynamic isomer whose structure (as the acac mononuclear complex) was confirmed by X-ray crystallographic analysis (equation 327)394. More recently, 1-aryl-substituted derivatives of this bicyclic methylenecyclopropane (equation... 

Unlike the alkyl and aryl-substituted methylenecyclopropanes discussed above, both cis- and franj-Feist s esters undergo chloropalladation with proximal 1,2-ring opening, to give isomeric n3-[3-chloro-l,2-bis(methoxycarbonyl)but-3-enyl]palladium complexes (equation 331)397. Formation of the but-3-enyl complexes is rationalized by sequential... 

The intermolecular addition of carbamates to 1,3-dienes (equation 147) under mild conditions has been described as well. The hydrothiolation of 1,3-dienes has also been reported. " Other related conjugate additions can be performed over methylenecyclopropanes (equation 148) with sulfonamides and the resulting product cyclizes by a second hydroamination of an olefin, finally yielding cyclic sulfonamides. This behavior is reproduced in a similar reaction for the ring opening of vinylcyclopropanes with sulfonamides. One more example in this group of reactions is the synthesis of dUiydrobenzofurans from aryl-allyl ethers. ... 

In the presence of Ni(0) catalysts, methylenecyclopropanes cyclodimerize at temperature as low as —15 °C. The chemoselectivity of these reactions strongly depends on the substitution pattern of the substrates. [2+2]-Cyclodimerizations are restricted to methylenecyclopropanes bearing no further substituents at the exo-cyclic double bond. The substitution pattern at the threemembered ring (R = alkyl, aryl) determines whether four-membered rings, five-membered ring or open-chain products (or a mixture of all those) are obtained. 

Aryl(methoxy)carbenes, generated photolytically from 3-aryl-3-methoxy-3//-diazirines, underwent addition to 1,1-dimethylallene to give methylenecyclopropane derivatives 1 (no yields or physical properties of the products were reported). ... 

In hindered or strained systems the yields are more variable. Thus, the yield of methylene product from 1-chloro-l-methyl-2,2-diphenylcyclopropane was only 39%. ° In a series of methylenecyclopropanes containing a bicyclic system with aryl bridgehead substituents, the yields in some cases were very poor (Table 1). In the absence of such substituents, however, the yields are generally very good. Thus, a 78% yield of pure 7-methylenebicyclo[4.1.0]heptane (13, n = 2) and a 85% yield of pure c/5-9-methylenebicyclo[6.1.0]nonane (13, n = 6) were obtained from the 1-chloro-l-methylcyclopropanes 12 derived from cyclohexene and (Z)-cyclo-octene, respectively. ... 

Eq. 58) have been prepared in this manner. Methylenecyclopropanes with aryl groups at the vinylic position undergo Ziegler-addition of n-BuLi under surprisingly mild conditions (Eq. 59). 

The starting materials are best prepared by the method of Makosza (for dihalocycloproi nra) or via halocarbene addition to alkenes Another attractive method for the preparation of ring-substituted methylene-cyclopropanes is the alkylation of lithiated methylenecyclopropane Until now, only trimethylsilylated > (Eq. 57) and a-hydroxyalkylated > derivatives (Eq. 58) have ban prepared in this manner. Methylenecyclopropanes with aryl groups at the vinylic position undergo Ziegler-addition of -BuLi imder surprisingly mild conditions (Eq. 59). 

Scheme 10.25 Nickel-catalyzed carbomagnesiation of methylenecyclopropanes with aryl Grignard s reagents proximal carbon-carbon bond cleavage [26].

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