Dimethyl sulfone, from hydroxyl

A one-pot procedure was developed by Otera et al. from p-cyclogeranylsulfone [32]. Its lithium salt reacted with 3,7-dimethyl-8-oxo-2,6-octadienyl acetate to the sulfone-alcohol. The hydroxyl group was protected to the MOM ether with MeOC Cl. Double elimination could be achieved with potassium MeOK to provide vitamin A in 50% yield, Fig. (12). 

Cyclizations. Cyclization of hydroxylated propargyl sulfones may involve isomerization to the corresponding allenyl sulfones which should behave as Michael acceptors. Access to the indolizidine skeleton by an intramolecular Michael reaction of 5-tosyl-4-pentenamide and subsequent alkylation at nitrogen and carbon is quite efficient. A synthesis of resorcinols from dimethyl acetonedicarboxylate and alkyl alkynoates involves a Michael reaction-Dieckmann cyclization sequence. 

From a theoretical point of view this is an extremely interesting reaction. The displacement of a hydroxyl group from a saturated carbon atom appears to be unknown in basic solution. The fact that amino-methane sulfonic acid can be isolated from the bisulfite addition product of formaldehyde on treatment with ammonia does not prove, of course, that a direct displacement, such as is indicated in XVI to XVII, actually occurred. Furthermore, it is quite clear that preliminary formation of an imine (XVIII) is not necessary for the reaction of aromatic amines with sodium bisulfite (steps XIX to XVIII to XVII, etc.). 1-Dimethyl-aminonaphthalene-4-sulfonic acid (XX) and l-aminonaphthalene-4-sulfonic acid (XIX) show similar reaction kinetics 16a when treated with sodium bisulfite, yet with the tertiary amine (XX) it is not possible to write an imino structure corresponding to XVIII. 

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