2- Phenyl- 1-methylenecyclopropane

Reactions of 2-phenyl- 1-methylenecyclopropane and of 2,2-diaryl-1-methylene-cyclopropane with hydrido complexes of Rh and Ir causes C-C bond cleavage of the three-membered ring (Scheme 87).130 The bond cleavage occurs via /3-alkyl... 

A cationic -allylpalladium complex with a diimine ligand, [(7r-allyl)Pd(4-Me-C6H4-N=CH-CH=N-C6H4-4-Me)](BF4) initiates ring-opening polymerization of 2-phenyl- 1-methylenecyclopropane at 80 °C (Eq. 41) [158, 159]. 

The polymer of 13C-labeled 2-phenyl-1-methylenecyclopropane by the same catalyst contains the isotope-labeled carbon exclusively at the exo-methylene group. The polymer consists of the 1-phenyl-2-exo-methylenepropan-1,3-diyl structure, exclusively. The 13C 1H NMR signals of the ipso carbon of the phenyl group are split into four due to the four triads, rr, rm, mr, and mm, based on comparison of the spectrum with that of poly(styrene-co-CO) with isotactic, syndiotactic, and atactic arrangement of the monomer units [160] (Scheme 16). Thus, the polymer produced from 2-phenyl-1-... 

Scheme16 Schematic drawing of the four triads of poly(2-phenyl- 1-methylenecyclopropane)...

The mechanism via 1,2-insertion is in contrast to the ring-opening polymerization of 2-phenyl-1-methylenecyclopropane by Pd complexes, where the polymerization proceeds via 2,1-insertion of the monomer into the 7r-al-lyl-Pd bond followed by /2-alkyl elimination. Cyanosilylation of 2-phenyl-1-methylenecyclopropane catalyzed by Pd and Ni complexes was reported to produce the acyclic and cyclic products depending on the metals [165], which also undergo the insertion of the substrate with and without ring opening. 

PdCl(Me)(bpy)/NaBARF initiates ring-opening copolymerization of 2-phenyl-1-methylenecyclopropane with CO (1 atm) at room temperature to produce a polyketone soluble in common organic solvent (Eq. 55) [181, 182]. 

Scheme 19 Mechanism of copolymerization of 2-phenyl-1-methylenecyclopropane with CO by Pd complexes...

The reaction obeys first-order kinetics with respect to the concentration of 2-phenyl-1-methylenecyclopropane at -30 to 0 °C. The first-order kinetics indicate that the rate-determining step of polymer growth is the insertion of methylenecyclopropane into the Pd-C bond rather than CO insertion, similar to the many alkene-CO copolymerizations reported so far. 2-Phenyl-1-methylenecyclopropanes having a Me or F substituent on the phenyl ring also undergo copolymerization to give the corresponding polyketones. 

Methyl chloride, phenyl-, 55, 94 Methyl isocyanide, p-tolylsulfonyl-[36635-61-71,58, 104, 106 Methyl sulfoxide [67-68-5], 59, 16 METHYLENECYCLOPROPANE [19527-12-91,57,36... 

X-ray structural analysis of 2,2-dimethyl-3-phenyl-l-methylenecyclopropane tungsten pentacarbonyl reveals an octahedral complex with characteristic W—C bond distance of 238 pm. The typical bond distances within the organic ligand are 138 (complexed C=C), 148 (proximal C—C), 154 (distal C—C) pm, compared e.g. with 140, 148 and 154 pm, respectively, for the Feist s ester iron complex analogue (see above). 

From a mechanistic point of view (see below) it is important to note that the chloropalladation of labeled 2,2-diphenyl-l-methylenecyclopropane-3,3-d2 gave only two isomeric complexes, with absence of the isomer in which both the phenyl and deuterium reside on the allylic moiety (equation 323). This allows the exclusion of a symmetrically bound >/4-trimethylenemethane (TMM) intermediate or rapidly equilibrating >/3-TMM species,... 

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-... 

Phenyl-substituted trimethylenemethane iron complexes can be obtained from the methylenecyclopropanes, XLVIIa and b, when reacted with Fe(CO)j [alternatively. 

Cycloaddition of phenyl azide (106, R = Ph) with methylenecyclopropanes (105) followed by photolysis of the primary products (107) yielded spiro compounds (108), in which the aziridine ring could easily be cleaved by acids leading to 109 and (equation 22). Alternatively, compound 108 (R = COOMe) was formed directly upon irradiation of methyl azidoformate (106) in the presence of excess 105 ... 

The primary cycloadducts, 2,4-dimethylene-N-phenyl-pyrrolidines, normally iso-merize to pyrroles during the reaction (Eq. 103). Only with geminally disubstituted methylenecyclopropanes, a-methylene-A3-pyrrolines are formed (Eq. 104)217). 

Many cyclopropyl chlorides and bromides have been converted to alkoxycyclopropanes by treatment with a strong base, in most cases potassium rerf-butoxide, in an appropriate organic solvent (Table 13). Under such conditions, hydrogen halide elimination takes place, yielding strained cyclopropene intermediates, which are trapped by nucleophilic attack of the alkoxide. Overall, a simple substitution occurs when a bond is formed between the alkoxide group and the carbon atom to which the halide was attached. This is the case when l-chloro-5-methyl-exo-6-phenyl-3-oxabicyclo[3.1.0]hexan-2-one (1) was reacted with potassium /ert-butoxide l-/er/-butoxy-5-methyl-ent/o-6-phenyl-3-oxabicyclo[3.1.0]hexan-2-one (2) was isolated in 94% yield.If a C-O bond is established at the other olefinic carbon atom, a C H bond is concomitantly formed at the carbon atom, to which the halide was attached. The result is a double substitution which is discussed elsewhere (see Section 5.2.1.3 ). When the substrate contains more than one halogen atom, several elimination reactions usually take place. Thus, treatment of 1 -bromo-2-chloro-2-methylcyclopropane (3) with an excess of potassium /er/-butoxide gave l-ter/-butoxy-2-methylenecyclopropane (4) in 30% yield. 

The same reaction took place with 1-phenyl-1-azaspiropentane obtained by nitrogen elimination from the adduct of phenylazide to methylenecyclopropane (see Section 5.2.3.1.2.3.1.). 

An example for the [2 + 2] cycloaddition of a N-N double bond to methylenecyclopropane is the reaction of 4-phenyl-4//-l,2,4-triazole-3,5-dione with rran.f-2,3-dimethylmethylenecyclo-propane. At room temperature, the [2 + 2] cycloadduct 18 was formed. 

---