Gold(I)-Catalyzed Formation of Bicyclo[4.2.0]oct-1-enes

Abstract

Gold(I) catalysts effectively promote the Cope rearrangement of acyclic 1,5-dienes bearing a terminal cyclopropylidene. When this methodology is applied to cyclic substrates an unexpected transformation occurs, resulting in the formation of a tricyclic compound incorporating a bicyclo[4.2.0]oct-1-ene core, a portion of which is found in a number of natural products. Density functional theory calculations (M06 and M06-2X) reveal insight into the mechanism and thermodynamics of this unique transformation.

Construction of Carbocycles from Methylenecyclopropanes

“…[107] Ther eactionw as then successfully employed in at otal synthesiso fpy-rovellerolactone. (102)]. [109] Thet hree-component [3+ +2+ +2] co-cyclizationo fc yclopropylidene-acetate 111,e nynes 223 and alkyne 224 led to 5-methylenecyclohepta-1,3-dienes 225 [Eq.…”

Recent advances in the chemical transformations of functionalized alkylidenecyclopropanes (FACPs)

“…29 Subsequently, they investigated ACP-containing cyclic 1,5-dienes 105 and disclosed an Au I -catalyzed ringexpanding cycloisomerization of 105 to produce the corresponding bicyclo[4.2.0]oct-1-enes 106 in good yields (Scheme 33). 30 Based on this result, novel ACP-bearing 1,5-enynes such as 107 were synthesized, and under the catalysis of PPh 3 AuNTf 2 , bicyclo[4.2.0]dienes 108 were obtained through a sequential 6-endo-dig-cyclization/ring expansion/net 1,2-hydrogen shift process (Scheme 34, eqn (1)). 31 It is worth noting that when FACPs 107 (R 2 = 1-propynyl) were treated with PPh 3 AuNTf 2 (10 mol%) in 1,2-dichloroethane at 50 1C, the expected bicyclic products 108 were not formed.…”

Gold‐Catalyzed Diastereoselective Cycloisomerization of Alkylidene‐Cyclopropane‐Bearing 1,6‐Diynes

“…[8] When this strain can be released under the careful guidance of a catalyst, it is possible for this potent thermodynamic driving force to be harnessed for otherwise unfavourable reactions. [9] Taking advantage of the ring strain relief strategy, our group recently reported the first enantioselective Cope rearrangement (gold-catalyzed) from achiral 1,5-dienes (Figure 2A). [9b] This success led us to investigate ACP containing cyclic 1,5-dienes and the discovery of a ring expanding cycloisomerization that yields tricyclic compounds incorporating the bicyclo[4.2.0]oct-1-ene core (Figure 2B).…”

“…[9] Taking advantage of the ring strain relief strategy, our group recently reported the first enantioselective Cope rearrangement (gold-catalyzed) from achiral 1,5-dienes (Figure 2A). [9b] This success led us to investigate ACP containing cyclic 1,5-dienes and the discovery of a ring expanding cycloisomerization that yields tricyclic compounds incorporating the bicyclo[4.2.0]oct-1-ene core (Figure 2B). [9c] Based on this result, we reasoned that gold catalysis of ACP-bearing 1,5-enynes such as 1a , would yield bicyclo[4.2.0] dienes ( 3 ) via a sequential 6-endo-dig-cyclization/ring expansion/net 1,2-hydrogen shift process (Figure 2C).…”

“…[9b] This success led us to investigate ACP containing cyclic 1,5-dienes and the discovery of a ring expanding cycloisomerization that yields tricyclic compounds incorporating the bicyclo[4.2.0]oct-1-ene core (Figure 2B). [9c] Based on this result, we reasoned that gold catalysis of ACP-bearing 1,5-enynes such as 1a , would yield bicyclo[4.2.0] dienes ( 3 ) via a sequential 6-endo-dig-cyclization/ring expansion/net 1,2-hydrogen shift process (Figure 2C). [10] However, when 1a (R 2 = 1-propynyl) was treated with 10 mol% PPh 3 AuNTf 2 in 1,2-dichloroethane at 50 °C, the expected bicyclo product 3 was not formed.…”