Electrocyclic reactions allyl-cyclopropyl anion

The electrocyclic reactions of 3-membered rings, cyclopropyl cation and cyclopropyl anion, may be treated as special cases of the general reaction. Thus the cyclopropyl cation opens to the allyl cation in a disrotatory manner (i.e., allyl cation, n = 0), and the cyclopropyl anion opens thermally to the allyl anion in a conrotatory manner (i.e., allyl anion, m = 1). Heterocyclic systems isoelectronic to cyclopropyl anion, namely oxiranes, thiiranes, and aziridines, have also been shown experimentally and theoretically to open in a conrotatory manner [300]. 

What is the preferred mode of rearrangement after electron transfer to (derivatives of) 102 or to 104 and 1051 Does the ring-opening reaction occur on the radical anion or the dianion stage These questions have been dealt with in a series of papers first by Bauld and coworkers 77). They are of general interest because the theoretical treatment of electrocyclic reactions of open-shell systems, as e.g. the cyclopropyl allyl radical rearrangement, led to ambiguous results 9,78 81). 

Consider the electrocyclic reaction wherein the allyl anion closes to form a cyclopropenyl tt anion (VIII). (The negative charge in the cyclopropyl anion may be thought of as resulting from double occupancy of a p-jr AO on the singly protonated carbon.) Sketch the orbitals being formed or destroyed in... 

Most of the tt 8-unsaturated ketones studied have been observed to form cyclopropyl acetates (47) under Clemmensen reduction conditions. The probable mechanism of this reaction involves the formation of an allylic anion which undergoes electrocyclic closure. Stereospecific reactions are observed when geometrical constraints are imposed. ... 

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