6,6 Dimethyl fulvene reaction

Mono- and l,3-di-ter/-butylcyclopentadienyllithium Li(Bu Cp) 4 (n = 1) and 5 (,n = 2) can be obtained directly by addition of methyllithium to 6,6-dimethyl fulvene and 2-/ert-butyl-6,6-dimethyl fulvene, respectively [27a]. Since the fulvenes themselves are easily accessible by base-induced condesation reactions [27b], this method offers a viable alternative to the usual metalation of the substituted cyclopentadienes 1 and 2 (Eq. 2). 

It is commonly accepted5,6,19 that unstable betaines IV (X = C) are intermediates of the cyclopropanation of olefins with the polar C=C bond by phosphorus ylides. However, only one compound of this type, viz., Me3P( + )-CH2-CMe2-C5H4( ) (1), synthesized in the reaction of dimethyl-fulvene with methylenetrimethylphosphorane, was isolated and characterized by multinuclear NMR spectroscopy.20... 

Interestingly, the reaction of dimethyl fulvene (R = Me) with 2H-azirine 132 in an ultrasonic bath (neat) yielded the alkylation product 138. The structure of 138 was unambiguously assigned by single crystal X-ray structure. A possible mechanism to account for the formation of 138 involves an initial [4- -2]-cycloaddition followed by a subsequent... 

An attempt to prepare the corresponding complex of 6,6-dimethyl-fulvene via the Grignard reaction resulted in hydrogen addition to yield the bis(77-isopropylcyclopentadienyl)cobalt cation (216). 

By contrast, if the important frontier orbital in a cycloaddition is the LUMO of the fulvene, and if the fulvene is to react as n2 or n6 component, it will now react as a ic6 component, because the largest coefficients are on C-2 and C-6. Thus with diazomethane, the LU (fulvene)/HO (diazomethane) interaction is probably closer in energy than the HO(fulvene)/LU(diazomethane) interaction (Fig. 4-72), and the adduct actually obtained (374)298 is the one expected from these considerations. Although reaction with a simple diene ought also to be dominated by the LU.(fulvene)/HO(diene) interaction (Fig. 4-72), nevertheless the observed294 product (376) from the reaction of dimethyl-fulvene (375) with cyclopentadiene has the fulvene acting as a n2 component rather than... 

Oxidative work-up of the reaction of C0CI2, RI1CI3 and IrClg with 6.6-diphenyl fulvene 159,161) and Grignard reagent produces the complexes (38) with 6.6-dimethyl fulvene (39) is obtained 159>. 

Further general route to 2-alkyl-2-butenolactones via the retro Diels-Alder reaction was developed, Fig. 5. [23], Hydrolysis of a known lactone (15), subsequent esterification with diazomethane, and treatment with dihydropyran afforded a stereoisomeric mixture of pyranyl ether. Alkylation of the pyranyl ether with various alkyl halide yielded alkylated products (16). The retro Diels-Alder reaction of 16 was performed by heating at 200-280 °C in a sealed tube to give 2-alkyl-2-butenolactones (17). The utility of the butenolactones was demonstrated by the synthesis of hinokinin (18) and dehydrolappaol A dimethyl ether (19). Similarly rather mild, simple synthesis of a-methylene-y-alkylbutyrolactones was deviced using dimethyl-fulvene as a protective group for the double bond, Fig. 6. [24]. The... 

Dimethylamine, reaction with phosphorus trichloride, 46, 42 f-Dimethylami nobenzaldehyde, conversion to 0,/9-dichloro- -dimethyl-aminostyrene, 46, 34 tn-Dimethylaminobenzoic acid, 47, 71 /5-Dimethylaminobenzoic acid, 47, 71 6.(Dimethylamino)fulvene, 47, 52 -Dimethylaminophenylacetic acid, 47, 71... 

Hong and coworkers have investigated the cycloaddition chemistry of fulvenes with a wide variety of alkenes and alkynes in great detail [191]. As one example, the reaction of 6,6-dimethylfulvene with benzoquinone is shown in Scheme 6.92. Under microwave conditions in dimethyl sulfoxide (DMSO) at 120 °C, an unusual hetero-[2+3] adduct was formed in 60% yield, the structure of which was determined by X-ray crystallography. The adduct is a structural analogue of the natural products aplysin and pannellin and differs completely from the reported thermal (benzene, 80 °C) Diels-Alder cycloaddition product of the fulvene and benzoquinone (Scheme 6.92) [191]. 

The preparation of fulvene enamines by the reaction of sodium cyclopent-adienide with dimethyl sulfate complexes of amides or lactams has recently been reported by several investigators [77, 78] (Eq. 22). 

Thiophene 1,1-dioxide did not undergo cycloaddition with electron-deficient dienophiles. In most of the cases the dihydrobenzothiophene derivative 109 was obtained as the major product. This shows that self-dimerization is faster than cycloaddition with a different molecule. In the case of dimethyl acetylenedicarboxylate (DMAD) and 4-phenyl-3//-l,2,4-triazole-3,5(4//)-dione (PTAD), the Diels-Alder adducts 111 and 112 of 109 were obtained <1997JA9077>. However, cyclopentadiene gave the Diels-Alder adduct 113 with thiophene 1,1-dioxide. The DMAD adduct 111 on thermolysis undergoes a retro-Diels-Alder reaction to give dimethyl phthalate and thiophene 1,1-dioxide. Azulene was isolated in the thermolysis of 108 in the presence of 6-(dimethylamino)-fulvene this was the result of a [4-1-6] cycloaddition of the thiophene 1,1-dioxide formed in the reaction followed by elimination of SO2 and dimethylamine (Scheme 28) <1999BCJ1919>. 

Azulene synthesis.10 The reaction between 6-(2-dimethylaminovinyl)fulvene (l)11 and dimethyl acetylenedicarboxylate (2) affords dimethyl 4,5-azulenedicarboxylate (3, 11 %) and dimethyl dimethylaminomaleate (4, ca 20%). 

Kurata, Kawase, and Oda s group developed a new one-pot fulvene synthesis the method uses the reaction of AiAf-dimethylformamide (DMF) or NJ -dimethyl chlorocarbamate (ClCONMe2) with aryl lithium reagents to provide fulvene derivatives without the isolation of rather unstable precursor ketones (Scheme 6.28a). As shown in Scheme 6.28a, CP anion and the corresponding ketone are generated in situ [61]. The procedure provides a fulvene oligomer 115 without isolation of the precursor ketone 116 (Scheme 6.28b) [62]. 

Similar reactions are found with dicobalt octacarbonyl and dialkyl fulvenes [32a]. Dimethylaminofulvene with iron pentacarbonyl gives several products, one of which is the unusual complex, 4.2, whose formulation is supported by the preparation of the dimethyl derivative, 4.3 [34 ]. 

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