Of hydroazulene

A stereoselective convergent synthesis of hydroazulenes 538 was also based on a tandem intermolecular cyclopropanation-Cope rearrangement sequence with predictable stereocontrol (equation 211)262. 

Recent studies on radical-induced cyclisation reactions have led to a simple, one step method for the preparation of hydroazulenes from appropriately substituted cyclopentanone precursors. Treatment of 1, for example, with triphenyltin hydride and AH3N in refluxing toluene gave 2 in 79% yield. 

Removal of the 0-substituted Fp group can be achieved by conversion into the cationic alkene-Fp complex using Ph3CPF6 and subsequent treatment with iodide, bromide or acetonitrile. Oxidative cleavage with ceric ammonium nitrate in methanol provides the methyl esters via carbon monoxide insertion followed by demetallation. The [3 + 2]-cydoaddition has been successfully applied to the synthesis of hydroazulenes (Scheme 1.11) [34]. This remarkable reaction takes advantage of the specific nucleophilic and electrophilic properties of V-allyl-, cationic t 5-dienyl-, cationic ri2-alkene- and ti4-diene-iron complexes, respectively. 

Conversely, the photoinduced ring-opening of cyclobutenes allows the construction of medium-sized hetero- or carbocycles, starting from bicyclic frameworks. Alkenes can undergo thermal (metal-assisted) or photochemical [2 + 2]-cycloaddition to a variety of alkynes the subsequent two-carbon ring-enlargement can serve as a versatile method for the preparation of hydroazulenes and dioxacyclooctadiene derivatives (Scheme 9.44) [74, 75]. 

As previously described, RCM is a powerful tool for the preparation of useful carbo- and heterocyclic intermediates. Almost all of the recent RCM reactions have been performed homogeneously with well-defined metal carbene complexes as catalysts. An example of the use of a heterogeneous catalyst in RCM is the synthesis of hydroazulenes such as 6 via RCM of highly functionalized diolefins (Eq. 17) catalyzed by CH3Re03/Si0i-Al703 and with heating under reflux at 80 °C [41]. 

Pyrolysis of (3) results in rearrangement to (4). Overall yields of hydroazulenes are satisfactory. ... 

A review has recently appeared describing the synthesis of hydroazulene sesquiterpenes through rearrangement of substituted hydronaphthalene precursors, including some syntheses of guaianolides from santonin (1)... 

Uses Solvent for lacquers, resins, emulsionbonding adhesives fragrance in cosmetics building block for synthesis of hydroazulenes prep, of dilongifolylborane (a chiral hydroborating agent)... 

Methylnaphthalene isomerises to 1-methylnaphthalene, with very little dimethylnaphthalene being formed, over various zeolites [93]. Silica gel has been used in the synthesis of hydroazulenes with good yields and selectivity [94]. 

Hydroazulenes. Startg. l,2-epoxy-2-methyl-3-methylenebicyclo[4.4.0]decane distilled slowly at 380-385°/4.5 mm under Ng through a column of sand cis-l-methyl-10-methylenebicyclo[5.3.0]decan-2-one. Y 75%. R. A. Kretdimer and W. J. Frazee, J. Org. Chem. 36, 2855 (1971) synthesis of hydroazulenes, review, s. J. A. Marshall, Synthesis 1972, 517. 

Although this certainly meets our expectations - if not to a large extent - the deprotonation of hydroazulene-ketone 69 with lithiumtriphenyhnethyl leading to mainly one enolsilylether is really remarkahle [32]. 

The synthesis of a compound may be the result of. serendipity. During the study of the formation of hydroazulene (equation 6) ... 

---