6- fulvene, reaction synthesis

Kerber et al. succeeded in the synthesis of the first iron complexes of isobenzo-fulvene. Reaction of the dibromide 89 with Collman s reagent (disodiumtetracar-bonylferrate) afforded isobenzofulvene complexes 90 and 91 in 4 and 2% yield, respectively. 90 is a trimethylenemethane system anellated to an intact benzene ring (Scheme 10.31) [83]. 

Oxidation of thiophene with peracid under carefully controlled conditions gives a mixture of thiophene sulfoxide and 2-hydroxythiophene sulfoxide. These compounds are trapped by addition to benzoquinone to give ultimately naphthoquinone (225) and its 5-hydroxy derivative (226) (76ACS(B)353). The further oxidation of the sulfoxide yields the sulfone, which may function as a diene or dienophile in the Diels-Alder reaction (Scheme 88). An azulene synthesis involves the addition of 6-(A,A-dimethylamino)fulvene (227) to a thiophene sulfone (77TL639, 77JA4199). 

This procedure illustrates formylation by N,N-dimethylamino-methoxymethylium methyl sulfate, a compound which can be produced readily by reaction of easily available materials. 6-(Dimethylamino)fulvene is a useful intermediate for the synthesis of various f used-ring nonbenzenoid aromatic compounds. 

The cobalt(I)-catalysed 6 + 2-cycloadditions of cyclooctatetraene with monosubsti-tuted alkynes produced monosubstituted bicyclo[4.2.2]deca-2,4,7,8-tetraenes in good yields.185 The 6 + 3-cycloaddition of fulvenes (145) with 3-oxidopyrylium betaines (144) formed 5-8 fused oxa-bridged cyclooctanoids (146,147), which can be manipulated by cycloaddition reactions to produce key intermediates (148,149) for the synthesis of fused cyclooctanoid natural products e.g. lancifodilactones (Scheme 38).186,187... 

Fulvalene zirconium(III) compounds, reactions, 4, 751 Fulvene chromium carbonyls, synthesis and characteristics,... 

Scheme 2 Synthesis of benzyl-substituted titanocenes through the hydridolithiation reaction of aryl-substituted fulvenes using superhydride...

Carbolithiation proved to be a very effective approach to highly cytotoxic titanocenes. The reaction of aryl or heteroaryl lithium species with 6-/V,/V-d i me thy I am i n o fulvene and subsequent transmetallation reaction led to dimethylamino-functiona-lised titanocenes with IC50 values of 6.8, 5.5 and 5.4 pM. Furthermore, this reaction proved to be tolerant to many substituents and to be a versatile tool for the synthesis of a wide variety of substituted titanocene dichlorides as seen in Scheme 3. 

Scheme 3 Synthesis of dimethylamino-functionalised titanocenes from the carbolithiation reaction of 6-/V,/V-dimcthylamino fulvene and aryl lithium species...

Scheme 5 Synthesis of achiral aryl and heteroaryl-substituted titanocenes from the carbolithia-tion reaction of 6-substituted fulvenes...

In several synthetic studies, cyclopropane derivatives were used as synthones or building elements for ring enlargement steps, e.g. reaction of enamines with cyclopropenone [65], synthesis of 2,3-dihydro-l,4-diazepine by thermal isomerization of 1,2-diamino-cyclopropanes [32] [66], and preparation of 3-amino-fulvenes from methylencyclopropenes with alkynamines [67]. 

An interesting example of the synthesis of dihydropyrans using hetero Diels-Alder (HD A) methodology is the formation of the polycyclic cage compounds 3 from fulvenes and the tetracyclic enone 2 <06SL3479>. A HDA reaction also features in the synthesis of (+)-8-methoxygoniodiol <06TL4545>. 

The mode of reaction of fulvenes with o-quinones varies with structure. As illustrated below, 7,7-disubstituted fulvenes (91) react with o-benzoquinone and alkyl substituted o-quinones to give bridged diones 90,91) (92). The regiochemistry of these reactions was determined by photobisdecarbonylation to 93. Subsequent oxidation with chloranil provided a synthesis of benzofulvenes (94). 

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