Bicyclo octenones

Ogasawara and coworkers have also published a complete series of threefold anionic domino reactions, all of which are based on an initial retro-aldol process. For instance, starting from chiral bicyclo[3.2.1]octenone 2-437, a formal total synthesis of (-)-morphine (2-445) [233] has been successfully performed (Scheme 2.103) [234]. Transformation of 2-437 into the substrate 2-488, necessary for the domino reaction, was achieved in seven linear steps. The domino process was then initiated by simply refluxing a solution of 2-438 in benzene in the presence of ethy-... 

This reagent is used as a Lewis acid catalyst for the intramolecular addition of diazo ketones to alkenes [130], The direct synthesis of bicyclo[3.2.1]octenones from the appropriate diazoketones using BF3 Et20 (Eq. 76) is superior to the copper-catalyzed thermal decomposition of the diazo ketone to a cyclopropyl ketone and subsequent acid-catalyzed cleavage [131]. 

The quinone monoketal 499 reacted with ( )-isosafrole in MeCN-MeOH containing 2,4,6-trinitrobenzenesulfonic acid (dry ice temp., 30 min) to afford dihydrobenzofuran 505 and bicyclo[3.2.1]octenone 506 in 42 and 20% yields, respectively. The former was further converted to two neolignans (507 and 508) (Scheme 96) . Herein, the dihydrobenzofuran 505 is formed from 509. 

Five- and six-membered rings can be prepared by this reaction [217], and the reaction has been plied to syntheses of natural products. Now the cycloalkeny-lation can be carried out with a catalytic amount of Pd(OAc)2 in DMSO under O2. The bicyclo[3.2.1]octenone 532, a partial skeleton of gibberellin, was obtained in 81 % yield by the cycloalkenylation of the silyl dienol ether 531 in DMSO using... 

A formal [5+2] cycloaddition starts from cyclohexenones and propargyl acetates (Scheme 5-181) (see also 2.4). In this case, bicyclo[3.2.1]octenones were produced in good yield and good overall stereoselectivity. 

Bicyclo[2.2.1]heptenones Bicyclo[3.2.1]octenones and Congeners Bicyclo[2.2.2]octenones Oxa-di-JC-methane Rearrangements in Polycyclic-Bridged P.y-Enones ... 

Ueyhara and co-workers have studied the photoreaction of a number of bicyclo[3.2.1]octenone systems, wherein the position of the chromophores is switched that is, the alkene chromophore is in the... 

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