Gold‐Catalyzed Migrations and Ring Expansions

Abstract

Gold complexes have been used to π‐activate alkynes, alkenes, and related moieties due to their strong affinity for these carbon systems. In this chapter we have summarized first, the most representative examples of gold‐catalyzed migrations occurring in propargylic systems and classified them according to the nature of the migrating group. In the second part, we have compiled the most relevant gold‐catalyzed ring expansions according to ring size. The current mechanistic understanding of these transformations is also presented.

Gold‐Catalyzed Cycloisomerizations of Functionalyzed Cyclopropyl Alkynes: the Cases of Carboxamides and Alcohols

“…In this context, we have demonstrated the critical effect of donor-acceptor substituents in the outcome of goldcatalyzed reactions of enynes. [8,9] Taking into account our previous experience, we wanted to assess the influence of donor-acceptor substituents in the cyclization of this kind of substrates. [6,7] On the other hand, alkynyl cyclopropanes have also served as useful starting materials for goldcatalyzed transformations.…”

“…, CDCl 3 ) d = 7.33 (d, J = 8.0 Hz, 2H maj + 2H min), 7.12 (d, J = 8.0 Hz, 2H maj + 2H min), 3.95 (dd, J = 11.6, 5.0 Hz, 1H, min),3.83 (dd, J = 11.9, 5.8 Hz, 1H, maj),3.65 (dd, J = 11.6, 8 4. Hz, 1H, min),3.57 (dd, J = 11.9, 8 9. Hz, 1H, maj),3.50 (s, 3H, min),3.45 (s, 3H, maj), 2.35 (s, 6H, min + min + maj), 20.3 (q, maj), 18.7 (q, min); LRMS: (EI) m/z (%) = 216 ([M] + , 1), 185 (100), 169 (29), 155 (68), 143 (95), 129 (47); HRMS: (EI) calculated for C 14 H 16 O 2 [M] + : 216.1150, found: 216.1154.…”

“…51 (m, 4H maj + 4H min), 4.01-3.93 (m, 1H min),3.85 (dd, J = 11.8, 5.8 Hz, 1H maj), 3.69-3.62 (m, 1H, min),3.57 (dd, J = 11.8,9.0 Hz, 1H maj),3.47 (s, 3H, maj),3.45 (s, 3H, min), 1.78-1.55 (m + bs, 4H, maj + min), 1.38 (dd, J = 10.0, 5.7 Hz, 1H maj), 1.25-1.18 (m, 1H min), 1.06-0.88 (m, 2H, maj + min); 13 C NMR data from the major isomer:13 C NMR (100 MHz, CDCl 3 ) d = 131.9 (2 CH), 130.2 (q, 2 J CÀF = 33.0 Hz, C), 126.2 (C), 125.3 (q, 3 J CÀF = 3.6 Hz, 2 CH), 123.8 (q, 1 J CÀF = 272.1 Hz, C), 88.7 (C), 84.4 (C), 63.3 (CH 2 ), 57.1 (C), 55.9 (CH 3 ), 29.0 (CH), 20.4 (CH 2 ); 19 F NMR (282 MHz, CDCl 3 ) d = À62.86 (min), À62.89 (maj); LRMS: (EI) m/z (%) = 270 ([M] + , < 3), 239 (100), 197 (24), 183 (14), 155 (15); HRMS: (ESI) calculated for C 14 H 13 F 3 NaO 2 [M + Na] + : 293.0760, found: 293.0759. 51 (m, 4H maj + 4H min), 4.01-3.93 (m, 1H min),3.85 (dd, J = 11.8, 5.8 Hz, 1H maj), 3.69-3.62 (m, 1H, min),3.57 (dd, J = 11.8,9.0 Hz, 1H maj),3.47 (s, 3H, maj),3.45 (s, 3H, min), 1.78-1.55 (m + bs, 4H, maj + min), 1.38 (dd, J = 10.0, 5.7 Hz, 1H maj), 1.25-1.18 (m, 1H min), 1.06-0.88 (m, 2H, maj + min); 13 C NMR data from the major isomer:13 C NMR (100 MHz, CDCl 3 ) d = 131.9 (2 CH), 130.2 (q, 2 J CÀF = 33.0 Hz, C), 126.2 (C), 125.3 (q, 3 J CÀF = 3.6 Hz, 2 CH), 123.8 (q, 1 J CÀF = 272.1 Hz, C), 88.7 (C), 84.4 (C), 63.3 (CH 2 ), 57.1 (C), 55.9 (CH 3 ), 29.0 (CH), 20.4 (CH 2 ); 19 F NMR (282 MHz, CDCl 3 ) d = À62.86 (min), À62.89 (maj); LRMS: (EI) m/z (%) = 270 ([M] + , < 3), 239 (100), 197 (24), 183 (14), 155 (15); HRMS: (ESI) calculated for C 14 H 13 F 3 NaO 2 [M + Na] + : 293.0760, found: 293.0759.…”

Gold-Catalyzed Synthesis of Small Rings

“… 641 Since then, the implementation of an impressive number of gold(I)-catalyzed protocols, mostly based on ring expansions and stepwise [2 + 2] cycloadditions, has rapidly expanded the field. 41 , 119 − 126 , 207 − 210 , 449 , 450 , 642 − 645 These novel methods enable construction of compounds ranging from simple rings to complex skeletons of natural products in an atom-economical manner.…”

“…7 , 8 , 41 , 646 Under gold(I) catalysis, a wide range of cyclopropane-embedded frameworks can undergo ring expansion to efficiently assemble substituted cyclobutanes. 41 , 644 , 645 , 647 , 648 …”