Carbene addition insertion, amide

A similar type of chiral rhodium porphyrin was found to be effective for the carbene-insertion reaction to olefins, where formation of the carbene complex takes place. Chiral rhodium complexes for catalytic stereoselective-carbene addition to olefins were prepared by condensation of a chiral aldehyde and pyrrole. Formation of the metal-carbene complex and substrate access to the catalytic center are crucial to the production of optically active cyclopropane derivatives. Optically active a-methoxy-a-(trifluoro-methyOphenylacetyl groups are linked witfi the amino groups of a,p,0L,p isomers of tetrakis-(2-aminophenyI)por-phyrin through amide bonds. Oxidation reactions of the... 

Sames et al. have reported the intramolecular cyclization of alkene-amide substrates catalyzed by [Ir(COE)2Cl]2 and the A-heterocyclic carbene ligand, N, A -bis-(2,6-diisopropylphenyl)-imidazolyl, via olefin insertion following oxidative addition of an sp C-H bond (Scheme 11) [117]. 

Intramolecularity was the next issue to be probed within the context of alkynyliodonium salt/nucleophile addition reactions.53 1 No prior history was available to guide us, and so the prospects for success remained uncertain. Of primary concern was the potential for iodonium salt/base destructive interactions in competition with the desired N-H deprotonation reaction. A substrate that bore some resemblance to key portions of the agelastatin precursor 33 was prepared (Scheme 6), compound 39. This species duplicated the alkynyliodonium/"amide" pairing of the real system, but it lacked the complex piperazine carbene trap of 33. The tosylimide (pre)nucleophile was proposed as a compromise between what we really wanted (an N-methyl amide) and what would likely work (a tosylamide). Simple treatment of 39 with mild base effected the desired bicyclization to afford the tosylimide product 41 in decent yield. A transition state model 40 for C-H insertion that features an equatorial phenyl unit might rationalize the observed sense of diastereoselectivity. So, at least for 39, no evidence for possible interference by iodonium/base reactions was detected. 

C(OMe) —CH3 with an ortho ester 175 (iii) the condensation of aryl- or alkylcarbene complexes with enolizable acid amides RCH2 —CONR2, a reaction involving insertion of the C—CN unit of the acid amide into the M=C bond 176 (iv) the insertion of an alkyne into the M=C bond of an (alkoxy)carbene complex 36,177 174 and (v) the base-catalyzed addition of an alcohol to a (l-alkynyl)carbene complex.96 168173 The last reaction has... 

---