Palladium‐Catalyzed Cyclopropanation of Strained Alkenes with 3‐Pinacolatoboryl‐1‐arylallyl Carboxylates

Abstract

The palladium‐catalyzed cyclopropanation of strained alkenes with 3‐pinacolatoboryl‐1‐arylallyl carboxylates was explored. The reactions proceeded smoothly under mild conditions, and the cyclopropanation products were obtained in good to high yields with high diastereoselectivities if CsF, 18‐crown‐6, and molecular sieves were used as additives. The reaction was hypothesized to proceed through the formation of a putative palladacyclobutene intermediate that needed to be considered to explain the observed stereochemistry.

Pd-Catalyzed Three-Component Reaction of 3-(Pinacolatoboryl)ally Acetates, Aldehydes, and Organoboranes: A New Entry to Stereoselective Synthesis of (Z)-anti-Homoallylic Alcohols

“…In our recent studies, we demonstrated the distinct reactivities of allylic gem -palladium/metalloid intermediates that could serve as C3 units in reactions other than allylation reactions. For example, we have reported the stereoselective cyclopropanation of strained alkenes by the Pd-catalyzed reaction of 1 (Scheme ) . Furthermore, a Pd-stabilized vinylcarbene intermediate B was formed from A , and it can be used in the carbene dimerization .…”

Versatile Reactivity of Metalloid‐Substituted π‐Allylpalladium Species

“…During the course of a study aimed at exploring the palladium‐catalyzed cyclopropanation of strained cycloalkenes with borylated allyl benzoates, the boryl group was found to affect the diastereoselectivity (Scheme 5). [32] The partially formed palladium‐complexed vinylcarbene species likely led to a decline in the diastereoselectivity. Interestingly, the combination of CsF and 18‐crown‐6 (18‐C‐6) as additives effectively promoted the cyclopropanation reaction and played a key role in the enhancement of diastereoselectivity in this reaction.…”

“…As described above, organosilyl‐substituted π‐allylpalladium species exhibited unique reactivities in addition to those in simple allylation reactions, such as stereoselective cyclopropanation of strained cycloalkenes [27,32] and carbene dimerization [33] . Critical to the efficacy of the latter process was the cognition that the ancillary ligand on palladium could be altered to the prevent formation of a putative palladacyclobutene species.…”