Cleaving reactions

Of some importance for the preparation of various dichlorophosphates are cleaving reactions of the P-O-P bridge in P2O3CI4, which quite often reacts completely with some organometallic oxides (36) 82) or suitably substituted ethers (37) 63) ... 

Rhodium-Catalyzed Nucleophilic Ring Cleaving Reactions of Allylic Ethers and Amines... 

Each of the four manganese ions cycles between Mn(II) and Mn(III) to generate the four electrons necessary. Had each pathway consisted of a single antenna and manganese centre the overall water cleaving reaction would take far longer and require a complex stepwise pathway consequently the entire photosynthetic... 

A widely applied strategy for the synthesis of various difunctionalized organic molecules, e.g. diols, dialdehydes, etc., relies on the oxidative cleavage of olelinic double bonds. Besides transition metal catalysis for asymmetric synthesis, periodate oxidation and ozonolysis are the standard tools for oxidative bond cleaving reactions. For economic and safety reasons, technically applicable alternatives to osmium-based chemistry and ozonolysis are of great interest. 

Further investigations on the field of oxidative bond cleavage even made single bonds accessible. Thus, biaryls 10 and 11 were similarly obtained by electrooxidation of 9,10-dihydrophenanthrene. Moreover, the cleaving reaction of benzylic carbons was also exploited in the synthesis p-tert-butylbenzaldehyde dimethyl acetale (3) starting from l,2-di-(p-ferf-butylphenyl)ethane (4, 1,2-DPTE) (Fig. 5.8) (Zollinger et al. 2004b). 

Carbon-Carbon Bond-Forming and Bond-Cleaving Reactions... 

Carbonyl groups are also utilized in catalytic C-C bond cleaving reactions. Under catalytic conditions, 8-quinolyl phenyl ketone 85 reacts with ethylene to give 8-quinolyl ethyl ketone 86 and styrene in quantitative yield [105]. Styrene is formed by cleavage of the phenyl-carbonyl bond, followed by ethylene insertion into the resultant phenyl-rhodium bond, and (3-hydride elimination. The accompanying formation of a rhodium-hydride complex is followed by incorporation of ethylene to furnish the ethyl ketone 86. 

The bond between the carbon atoms a and (3 to a C-C double bond can be broken by a transition metal with formation of a Jt-allyl intermediate providing the driving force. Whereas stoichiometric reactions of this sort are yet to appear, jt-(allyl)metal intermediates are occasionally involved in catalytic C-C bond cleaving reactions. The nickel catalyzed skeletal rearrangement of 1,4-dienes involves the formation of an olefin coordinated Jt-(allyl)nickel complex (99) [118]. 

Interest in ring cleaving reactions of oxabicyclic compounds experienced significant growth in the late seventies as a consequence of the development of new methods to assemble oxabicyclo [3.2.1] compounds. Ring opening of oxabicyclo [2.2.1] substrates also underwent a renaissance in concert with... 

---