Ring Enlargements. IV. Steric Influences in Diazomethane-Carbonyl Reactions. The Reaction of cis- and trans-α-Decalone with Diazomethane^1,2

Ethylene Oxides

“…Treatment of a,&unsaturated ketones with diazomethane generally gives pyrazolines, as with a,fi-unsaturated aldehydes.485~ 693 Although it has recently been found possible to cause addition of diazomethane directly to the carbonyl function of such compounds through the use of catalytic amounts of boron trifluoride,8209 879 it is not possible as yet to prepare anything but a homologous a,p-unsaturated ketone in this manner.…”

“…693 Evidence for the linear nature of diazoalkanes has been obtained by various types of physical measurements, including electron diffraction and infrared spectroscopy.~87~ 365-1432…”

“…It is evident that in response to the demands of the substrate, and probably under the influence of solvents as well, the carbon atom of diazomethane can sustain a negative charge long enough to allow it to function as a nucleophile, in the manner of more conventional carbonyl reagents. 693 Evidence for the nucleophilic character of diazomethane in this condensation can be drawn from the enhanced reactivity of chlora142~ 1139,1537 and a-chloroacetone41 relative to acetaldehyde and acetone respectively, and of p-nitrobenzaldehyde411 44 relative to benzaldehyde.169~ 118091636 In the former, halogen atoms exert an electron-withdrawing effect by simple induction, thereby enhancing the positive character of the carbonyl carbon. In the latter, the nitro group operates inductively and by resonance as well to increase the nucleophilic susceptibility of the carbonyl function.…”

“…It was amply emphasized above that the formation of homologous ketones is the principal competing reaction in this condensation.4859 693 To explain this observation it has become customary to invoke a transient intermediate zwitterion, termed by Arndt and Eistert433 485 a ' diazonium betaine ', which can collapse into an epoxide with attendant nitrogen expulsion, or can undergo rearrangement to one or two possible carbonyl compounds. The process may be represented schematically as shown in Eq.…”

“…693). It (693) appears, therefore, that if nucleophilic attack by SO$ion is slow with respect to acid-catalyzed rearrangement to a carbonyl compound, the product secured from treatment of an epoxide with aqueous sodium bisulfite may well be a bisulfite addition product. Such an adduct has also been isolated from 1,1-diphenylethylene 0xide,Q42 but no other illustrations exist so far in the literature.…”