Ketones, cyclic ring expansion with

The acylation of enamines derived from cyclic ketones, which can lead to the acyl ketone or ring expansion (692-694), was studied by NMR and mass spectroscopic analysis of the products (695,696). In a comparative study of the rates of diphenylketene addition to olefins, a pronounced activation was observed in enamines (697). Enamine N- and C-acylation products were obtained from reactions of Schiff s bases (698), vinylogous urethanes (699), cyanamides (699), amides (670,700), and 2-benzylidene-3-methylbenzothiazoline (672) with acid chlorides, anhydrides, and dithio-esters (699). 

Acetates can be used instead of alkenes. Cyclic ketones undergo ring expansion to give a-hydroxyketone precursors. Oxiranes ring-open with siloxymethylation at ambient temperature and CO pressure. ... 

Rearrangements. Cyclic ketones undergo ring expansion on reaction with hydroxyalkyl azides." Regioselectivity is dependent on steric and electronic factors. Beckmann rearrangement of ketoxime carbonates has been observed at room temperature. 

The well-known reaction leading to ring expansion of cyclic ketones has been applied to derivatives of oxo sugars in an attempt to develop a new route to novel deoxy sugars. By treatment with diazomethane both a five-membered (42) and a six-membered (26) sugar ring have been expanded by insertion of a methylene group. 

Treatment of a cyclic ketone with diazomethane is a method for accomplishing a ring-expansion reaction. For example, treatment of cyclohexanone with diazomethane yields cycloheptanone. Propose a mechanism. 

The Michael addition of cyclic a-nitro ketones to acrolein or methyl vinyl ketone followed by reduction of the carbonyl group and treatment with base results in the ring expansion (Eq. 

Ring expansion of cyclic ketones via nitro-aldol reaction of a-nitrosulfides followed by treatment with A1C13 has been reported (Eq. 7.35).36... 

Three-cmbon ring expansionThe cyclic p-keto esters 1 with a 4-oxopentyl group at the a-position do not undergo the expected aldol condensation on treatment with KOC(CH3)3 in DMSO, but undergo ring expansion to medium-size ketones (2). The reaction may involve aldol and retro-aldol condensation. A similar... 

C. Ring expansion of cyclic ketones with diazo compounds... 

Ring expansion of cyclic ketones 8-24 Treatment of cyclic boranes with CO 8-29 Cyclization of conjugated dienes and trienes... 

Ring expansion of cyclic ketonesA new method for expansion of cyclic ketones to the expanded a-dithioketals involves addition of (CH3S)sCLi followed by treatment of the adduct with tetrakis(acetonitrile)coppcr(l) perchlorate or tetra-fluorohnrutc.2... 

Finally, ring expansions of cyclic ketones are an important method for the preparation of carbocyclic systems. Diazoalkanes allow this reaction to occur and involve C—C bond formation. When combined with carefully chosen organoaluminum compounds, this process can be performed in a highly stereoselective fashion (equation 148)541. 

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