The adamantane rearrangement of 1,2‐trimethylenenorbornanes. Part V. Rearrangements of 1,2‐trimethylenenorbornanes initiated by regioselective formation of carbocation centers at C(2) and C(6)

Abstract

The behaviour of the regioselectively generated carbocation centers at C(2) and C(6) in 1,2-trimethylenenorbornanes was investigated in order to study the occurrence or absence o f a degenerate rearrangement EF?M in the adamantane rearrangement of both 1,Zendo-(1) and 1,2-exo-trimethylenenorbornane (2) to 2-endo,6-endo-trimethylenenorbornane (3). A degenerate rearrangement E e M is inevitably involved inasmuch as a 1,2-trimethylenenorborn-2-yl cation E not only is formed directly as manifested by the conversions of the reactants 4 (C(2), C(3)-olefin) and 6 (C(2), C(3')-olefin), but also indirectly (via F-E) if the leaving group at C(6) to be ionized occupies the endo-position (dendo-alcohol 8). No degenerate rearrangement E@M is operative starting from reactants that lead directly to a 2,6-trimethylenenorborn-2-y1 cation G ; this is the case with both the ionization of the 6-exo-alcohol 10 having the leaving OH-group in a stereoelectronically favoured configuration to undergo simultaneous C(I),C(2)-bond migration (-G) as well as the protonation of the olefin 13 which is followed by the same reaction pathway.1. Introduction. -In the adamantane rearrangement of both 1,a-endo-(l),) and 1,Zexo -trimethylenenorbornane (2)2) to 2-endo,6-endo-trimethylenenorbornane (3)*), a degenerate rearrangement (EsM3); Scheme 2) is involved as verified from treatment of D-labelled 1 ,2-endo -, 1,2-exo-, and 2-endo,6-endo -trimethylenenorbornane (D-labelled 1,

The Adamantane Rearrangement of Tricyclo[4.2.2.01,5]decane to Tricyclo[5.3.0.04,8]decane

“…'H-NMR: 1.15-1.45 (m, 4 H); 1.15-1.35 (m, among others Jgem = 12, J(3c(9), 4) = 7, H-C(4)); 1.5-1.8 (m, 3 H); 1.52 (dd, J,,, = 13.5, J(2'(*), 3C'9') = 2.5, HC@-C(2)); 1.60 (s, HOCi8'-C(3)); 1.8-2.05 (m. 3 H); 1.89 (dd, JgCm = 13.5, J(2' ", 3c(9)) = 9, Hci9'-C(2)); 1.95-2.05 (m, among others J em = 12, J(3C(9',4') = 7, J(4',5) = 7, H-C(4')); 4.77 (dtd, J(2c(9), 3Ci9)) = 9, J(3c(9),4) = J(3c(9),4') = 7, J(2c(8),3Cw)) = 2.5, HC(9'-C(3)). MS: 152 (14, M"), 134 (23), 124(15), 123 (15), 119 (12), 109 (12), 108 (58), 106 (23), 105 (16), 96 (9), 95 (26), 94 (9), 93 (42), 92 (12), 91 (17), 81 (23), 80 (loo), 79 (37), 77 (ll), 67 (19), 55 (12), 41 (13).…”

“…'H-NMR: 1.3-1.45 (m, H,,,-C(7), H,,d,-C(lO)); 1.7-1.85 (m, 2 H-C(8), 2 H-C(9)); 1.9-2.1 (m, Hex,,-C(7), Hcxo-C(lO)); 2.28 (s, 2 H-C(2)); 2.90 (1, J(6,7exo) = J(6,lOexo) = 4, H-C(6)); 5.62 (s, H-C(4)). MS: 148 (48, M"), 133(5.5), 120 (100), 119(19), 105(14),92(36),91 (57),79(10),78(6),77(8),65(11),63(6), 53(7), 52 (6),51 (ll), 50 (5), 41 (7), 39 (21), 28 (12…”

“…'H-NMR(12): 1.15-1.65, 1.8-2.2 (2m, 12 H); 5.69,6.04 (2m, wl,,~l0each,H-C(2),H-C(3)). MS: 134(9,MC'), 119(5.5), 106(15), 105(100),91 (19),79(15),78 (12).…”

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

“…Illustrative of this point is 1,2-trimethylenenorbornane 2 , a structural motif that occurs in numerous synthetic precursors to abiotic adamantanes [4] and [3.3.3]-propellanes, [5] in addition to numerous classes of sesquiterpene natural products, including the cedrenes, [6] and the pentalenene/isocomenes (Figure 1). [7] The traditional approaches to 2 have relied on intramolecular [4+2] cycloaddition reactions, [4–7] but the laborious process for preparing the needed starting materials has limited the applicability of 2 in complex molecule synthesis.…”

“…[7] The traditional approaches to 2 have relied on intramolecular [4+2] cycloaddition reactions, [4–7] but the laborious process for preparing the needed starting materials has limited the applicability of 2 in complex molecule synthesis. Efficient methods for the construction of the tricyclic ring system of 2 under catalyst control are thus desirable and would enable their application in synthesis.…”