6,6 Dimethyl fulvene

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>. 

Diphenyl-fulven reagiert mit Natrium/Naphthalin in Tetrahydrofuran bei -78° zu einem Gemisch aus 34% d.Th. 2- und 13% d.Th. 1 -Diphenylmethyl-cyclopentadien-(l,3)b, wahrend 6,6-Dimethyl-fulven unter C,C-Verknupfung (s. S. 676) reagiert. 

Zur reduktiven Dimerisierung von 6,6-Dimethyl-fulven mit Natrium/ Naphthalin/ THF/ -78° s. Lit.4. 

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... 

Fulvene-type enamines, which possess some nonbenzenoid aromatic character, have been synthesized by treating cyclopentadienylsodium with an amide-dimethyl sulfate eomplex (117aJ17b) or quaternary pyridinium salts (117c). One of the simplest ones produced is 6-(dimethylamino)fulvene (117a,117d). 

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... 

Of the fundamental nonalternant hydrocarbons, only two prototypes were known about fifteen years ago azulene (XI, Fig. 5), the molecular structure of which was determined by Pfau and Plattner and fulvene (XIX) synthesized by Thiec and Wiemann. Early in the 1960 s many other interesting prototypes have come to be synthesized. Doering succeeded in synthesizing heptafulvene (XX) fulvalene (XXI) and heptafulvalene (XXIII). Prinzbach and Rosswog reported the synthesis of sesquifulvalene (XXII). Preparation of a condensed bicyclic nonalternant hydrocarbon, heptalene (VII), was reported by Dauben and Bertelli . On the other hand, its 5-membered analogue, pentalene (I), has remained, up to the present, unvanquished to many attempts made by synthetic chemists. Very recently, de Mayo and his associates have succeeded in synthesizing its closest derivative, 1-methylpentalene. It is added in this connection that dimethyl derivatives of condensed tricyclic nonaltemant hydrocarbons composed of 5- and 7-membered rings (XIV and XV), known as Hafner s hydrocarbons, were synthesized by Hafner and Schneider already in 1958. 

More recently, a very efficient asymmetric carbolithiation of N,N-dimethyl-aminofulvene 30, leading to a chiral cyclopentadienide anion, was reported by Hayashi et al. [6] for the synthesis of chiral metallocenes (Scheme 6). By adding an aryl lithium such as 31 complexed with a chiral ligand on fulvene 30, a cyclopentadienide ion 32 bearing a stereogenic center at the a position was generated. This anion was reacted with [RhCl(nbd)]2 to yield... 

Dimethyl anthracene and diphenyl isobenzofuran form remarkably stable233 cyclopropanone derivatives (353/354), whilst with other diene components (butadiene, tetracyclone, and fulvene) the primarily formed Diels-Alder adducts either suffer ketalizing attack of the solvent (356 - 357, 359 - 358/360) or undergo irreversible changes such as decarbonylation to 362 or rearrangement to 355. 

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). 

For relief and reassurance, Table 5.13 shows the relative energies of some isomers calculated at modest levels, namely HF/3-21G1 1, HF/6-31G, and MP2/6-31G. For a reality check, we also see values from G3(MP2) and experiment (experiment fulvene/benzene, [229/230] cyclopropane/propene, [231/231] dimethyl ether/ethanol, [232/233] methylcyclopentane/cyclohexane, [230/234]). The energy differences chosen for this illustration are enthalpy differences, because differences in heats of formation yield these, and heats of formation represent the most extensive compilations of experimental energy quantities relevant to our... 

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>. 

HMn(CO)s has been photolysed in Ar and CH4 matrices and this produces CO and HMn(CO)4, a compound having a C, structure. Narrow band photolysis also leads to small amounts of a second isomer of HMn(CO)4 which has a C4 structure. PhMn(CO)5 has been observed to photoreact with 6,6-dimethyl- and 6,6-diphenylfulvene to give Ph(CO)4Mn(T -fulvene) complexes. Irradiation of RMn(CO)jL2 [10 R = H or Me, L = P(OPh)j] and of MeMn(CO>4L in benzene induces formation of the orthometallated products (11). These arise by formation of a 16-electron intermediate which in-tramolecularly activates a C-H bond of Ph in PCOPha). ... 

---