Ring expansion cycloalkanones

Reduction, carboxyl groups, 56,83 Reduction of a,0-unsaturated p-toluene-sulfonyl-hydrazones to alkenes, 59,42 Reductive alkylation, 56,52 Reductive cleavage, 56, 101 Resolution of amines, 55,80, 83 Rexyn 201,55,4 Rhodium(III) oxide, 57, 1 Ring contraction, 56, 107 Ring expansion of cycloalkanones to cycloalkenones, 59, 113... 

ONE-CARBON RING EXPANSION OF CYCLOALKANONES TO CONJUGATED CYCLOALKENONES 2-CYCLOHEPTEN-l-ONE... 

Ring expansion.1 The adducts (2) of cycloalkanones with 1 on reaction with methyllithium or wc-butyllithium at 0° rearrange to ring-expanded a-phenylthio ketones. 

Radical-mediated ring expansion of 2-halomethyl cycloalkanones. 

The procedure described is a simple, rapid, and convenient method for conversion of n-sized cycloalkenones into n+4 alkenolides. Significant but limited progress has been reported in the recent literature toward the preparation of medium and large ring lactones via ring-expansion reactions. One of the most notable and useful developments in this area involves conversion of a cycloalkanone into a bicyclic vinylic ether which is oxidatively cleaved to form a ring-enlarged keto lactone.3... 

Ring expansion of cycloalkanones.1 The hypoiodite reaction can also be used for a four-atom ring expansion of cyclic ketones via the corresponding lactols (cf., 13, 150). 

Scheme II/6. Ring expansions of cycloalkanones by diazo reagents.

Ring enlargement reactions also take place in 2-oxocycloalkane-l-carbonitri-les substituted in 1-position by an co-alkylester or ketone [17]. The introduction of cyano groups into the a-position of cycloalkanones can be carried out in CH2C12 with C1S02NC0 in dimethylformamide [18]. Two and three carbon atom ring expansion reactions are possible by this method. In most cases the yields are low, which is in contrast with the results of the lactonisation (compare... 

In a free radical ring expansion reaction discovered quite recently [24] [25], a methyl or ethyl cycloalkanone-2-carboxylate was first alkylated with methylene-dibromide [24] or bromomethylphenylselenide [25], Scheme VII/11. 

Both materials were isolated in approximately 30 % yield. The iodo compound VII/175 was then reduced photochemically with tributyltinhydride to give 15-pentadecanolide [114]. Experiments with different cycloalkanones (five- to eight-membered) and different lengths of the side chain (two and three methylene groups) showed that this reaction can be used for the synthesis of several medium sized lactones [75] [80] [114]. Under similar reaction conditions, lactols can also undergo ring expansion reaction [115]. The substrates (steroidal lac-... 

Riiedi et al. discovered a novel and efficient two-carbon ring expansion of vinylcycloalkanones 148 (Scheme 32). Precursors with n = 9 to 15 were ther-molysed at 600-630 °C to generate diradical intermediates, which took part in intramolecular recombinations to yield ring-expanded y,8-imsaturated cy-cloalkanones 149 [120]. In each case a mixture of E and Z isomers was obtained. Thermolysis of the 12-membered-ring ethynyl-substituted cycloalka-none 149 yielded a novel 14-membered-ring allenyl-cycloalkanone 150 via an analogous mechanism. 

Cycloalkanone derivatives can be prepared from cycloalkenoxiranes by ring-expansion as illustrated in Eq. 324.1 ... 

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