Formal (4+1) Cycloaddition of Methylenecyclopropanes with 7‐Aryl‐1,3,5‐cycloheptatrienes by Triple Gold(I) Catalysis

Abstract

7-Aryl-1,3,5-cycloheptatrienes react intermolecularly with methylenecyclopropanes in a triple gold(I)-catalyzed reaction to form cyclopentenes. The same formal (4+1) cycloaddition occurs with cyclobutenes. Other precursors of gold(I) carbenes can also be used as the C 1 component of the cycloaddition.

NHC/Nickel(II)‐Catalyzed [3+2] Cross‐Dimerization of Unactivated Olefins and Methylenecyclopropanes

“…And it avoids issues like competitive MCP-opening by [2+2] or [3+3] dimerization, or insertion of MCP into Ni 0 , and rearrangements into cyclobutene when using Au I , all of which are related to other fascinating MCP reactivities. [5,11] Notably, control experiments showed that the facile formation of 3 was not a result of NHC accelerated Ni 0 oxidative addition of 1, and this observation is distinctly different from the in reactivity assumed for using NHC in place of P. Our results suggest an efficient rearrangement of 1 catalyzed by NHC/Ni II , thus achieving unparalleled reactivity, new scope, high selectivity, and efficiency.…”

Gold(I)‐Catalyzed Cycloisomerization of ortho‐(Propargyloxy)arenemethylenecyclopropanes Controlled by Adjacent Substituents at Aromatic Rings

“…Tran-sition state TS3' is higher in energy than transition state TS3 by 2.6 kcal mol À1 .T hese calculated resultsa lso show that all intermediates alongP ath 1a re more stable than the corresponding intermediates on path 2, and thus the Path 1i sa lso thermodynamically favorable. Therefore, we concludet hat the reaction of substrate 1a along Path 1t akes place more easily,a ffording the corresponding product 2a.H owever,i f3d is utilized as substrate, it is more difficultf or the reactiont oo ccur along Path 2; presumably,i tp roceeds more easily by the reaction processs hown in Cycle II involving ring enlargement of methylenecyclopropane and [2,3]-sigmatropic rearrangement, which are already well-knowna nd have been reported by Fürstner and Aiessa,[12e] Echavarren et al, [19] Ta ng et al [22e] Herein, we performed no further studies on the reaction pathway in Cycle II.…”

Construction of Carbocycles from Methylenecyclopropanes

“…For example, in the Au‐catalyzed [4+1] cycloaddition of monosubstituted MCPs 1 with aryl‐substituted cyclohepta‐1,3,5‐trienes 122 affording cyclopentenes 123 [Eq. (53)], the substrate 122 was the benzyl source and it led to active benzyl Au carbene intermediates in the reaction process. On the other hand, when catalyzed by Au, MCPs 1 rearranged to cyclobutene intermediates and then reacted with the in situ generated benzyl Au carbenes to give cyclopentenes 123 as the final product.…”