Reactions of Cyclopropenes with Organoaluminum Compounds and Other Organometallic Compounds:  Formation of Ring-Opened Products

Abstract

Reactions of 1-ethylspiro[2.5]oct-1-ene and triethylaluminum furnish a product that results from addition of triethylaluminum to the double bond with opening of the three-membered ring to form an allylic organoaluminum compound and a second product that results from addition of this allylic organoaluminum compound to the cyclopropene double bond. Reactions of spiro[2.5]oct-1-ene with triethylaluminum furnish two products resulting from addition to the cyclopropene double bond, one of triethylaluminum and the other of an allylic organoaluminum compound formed by addition of triethylaluminum to the cyclopropene double bond with opening of the three-membered ring. Reactions of the spiro compounds with triethylboron, triethylgallium, diethylzinc, or diethylcadmium also furnish rearrangement products, but reactions with diethylmagnesium or ethyllithium furnish only addition products.

Advances in tandem reactions with organozinc reagents

“…87 Tandem carbozincations and electrophilic trapping of spiro [2.5]oct-1-enes with Et 2 Zn have also been reported by the group of Richey. 88 Normant and co-workers reported, simultaneously with others, the carbometallation reaction of the a-(N-alkenylamino)esters 141 (Scheme 38). [89][90][91][92] The Reformatsky-type reagent 142, obtained by the deprotonation of a-aminoester 141 followed by transmetallation with ZnBr 2 , underwent intramolecular addition leading to alkyl zinc species 143, which provided the pyrrolidines and piperidines 144 in moderate yields upon hydrolysis.…”

Directed Cu(I)-Catalyzed Carbomagnesiation of 1-Arylcycloprop-2-ene-1-carboxamides En Route to Densely Substituted Functionalized Cyclopropanes

“…The opposite regioselectivity resulting from overwhelming sterics created by an extremely bulky bis(tert-butyl)magnesium reagent was shown on a single example and required relatively harsh conditions causing partial cleavage of the cyclopropyl ring. 22 We reasoned that strong coordination of the organometallic moiety to a sterically demanding carboxamide group would amplify the effect of steric factors and divert the regioselectivity of carbomagnesiation toward predominant formation of the alternate cyclopropylmetal species 40 (scheme for Table 4). To test this idea, we treated nbutylsubstituted cyclopropene-3-carboxamide 38a with various Grignard reagents.…”

C–C Bond Cleavages of Cyclopropenes: Operating for Selective Ring-Opening Reactions

“…However, these reactions show a strong dependency on the substituents of cyclopropene . For instance, it was shown in 2007 that for 1,2,3-triphenyl­cyclopropene ( 178 ), the reaction was completely selective to alkene 256 (Scheme B, right). , These examples were illustrative with respect to reactivity but, overall, inoperable from a synthetic standpoint.…”