Bicyclo hexanone

The photochemical interconversion of cis- and tra/w-5,6-diphenyl-bicyclo[3.1.0]hexanones has been extensively studied by Zimmerman, Hancock, and Licke.<77) Using isotope dilution analysis, these workers obtained very accurate quantum yields for the various photochemical processes involved in this reaction ... 

The photorearrangement of cyclohexenones to bicyclo[3.1.0]hexanones (type A process) has been extensively studied (55 65> ... 

In a related reaction, tin(IV) chloride activated the bicyclo[3.1.0]hexanone system 10 and made it susceptible to an intramolecular nucleophilic attack by a methoxy-substituted phenyl ring. Since this reaction has been shown to occur stereoselectively, a concerted mechanism has to be assumed. 

Cyclic enones, such as substituted cyclohex-2-enones or cyclohexa-2,5-diones, also undergo sigmatropic photorearrangement to form bicyclo[3.1.0]hexanones (lumiketones) or bicyclo[3.1.0]hex-3-en-2-ones, respectively, for which both concerted and stepwise (biradical) reaction mechanisms have been proposed.640,641,770 For example, a [l,2]-shift concurrently with the ring contraction (termed the type A reaction) is observed upon irradiation of the methylphenyl derivative 159 in polar solvents, whereas phenyl migration (termed the type B reaction) predominates in nonpolar solvents (Scheme 6.70).771,772 The reactions are believed to proceed via both the n,n and n,Tt triplet ketone states. In the presence of alkenes, cyclic enones may readily undergo a competitive photocycloaddition reaction (Section 6.1.5). 

Intramolecular cyclopropanation reactions give access to bicyclic compounds, with, most commonly, the three-membered ring fused to a five- or six-membered ring. Metal-catalysed decomposition of the diazocarbonyl compound 119 gives the xo-bicyclo[3.1.0]hexanone 120 (4.95). The reaction is stereospecific, and the Z-isomer of 119 gives the endo diastereomer of the product. 

Two allyl cyclopropane-c s in equivalent amounts are actually observed to be formed. In the mercury sensitized decomposition of 5,5-dimethyl bicyclo [2.1.1] hexanone-2 (XXXI), the only cyclic hydrocarbons found are those derived from cyclopropane (38). 

Several studies 1 -206.212-214 demonstrated that the cleavage of the cyclopropyl bond is a stereocontrolled process. The stereochemical aspects of the addition of lithium dimethylcuprate to a bicyclo[4.1.0]hexanone derivative have been studied and reported. ... 

When bicyclo I 3.1.01 hexanone and bicyclo 14.1.01 heptanone are substituted by electron-withdrawing groups at C(P) a ring-expanded product is formed. Similarly, the irradiation of bicyclo 15.1.01 octanone and bicyclolo.I.olnonanone in the presence of EtjN led to the ring-expanded products (Scheme 62). 

In an aptly titled paper Herz et describe unexpected rearrangements of photolevopimaric acid derivatives. Among a wealth of chemical reactions discussed it appears that the exo-bicyclo[2,2,0]hexanol (575), derived from methyl levopimarate by hydroboration-oxidation, is rearranged during Jones oxidation to the bicyclo[2,l,l]-hexanone (576), contrary to a previous report. A mechanism is proposed. 

Diazoalkanes serve as useful precmsors to bicyclo[3,l,0]hexanones, which on thermolysis lead to 3-substituted-2-methoxycarbonylcyclopentanones, a system not readily prepared by 1,4-additions owing to the difficulty of preparing the requisite enone (Scheme 65). ... 

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