Carbonyl functionality, retention

More recent work in this series demonstrated that a carbonyl group can be interposed between the side-chaincarrying aromatic ring and the ethylene function with full retention of activity. Claisen condensation of benzoate with 2-tetralone affords the e-diketone Reaction of... 

Carbenes or carbenoids have also been reported to deoxygenate epoxides. To generate these species, dimethyl diazomalonate/rhodium(II) acetate and 9-diazofluorene 44 have been employed both reagents show high stereoselectivity. For example, ciJ-2-butene oxide is converted to cir-alkene with more than 93% retention under irradiation (350 nm) using 9-diazofluorene, and functional groups, such as carbonyl, can survive using diazomalonate and rhodium(II) acetate (equation 49). 

Reactions of acetylene with retention of the triple bond lead to valuable building blocks for synthesis, which can be made to undergo further functionalization. In industry, the most important examples of ethynylation are C-C linkages by addition of acetylene to carbonyl compounds. 

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