Synthesis of a Trithienocyclotriyne

Cross‐Coupling Reactions to sp Carbon Atoms

“…Another advantage of [Pd(PPh 3 ) 4 ] is that the reductive elimination step required of [Pd(PPh 3 ) 2 Cl 2 ] to form 7 is avoided, so very little or none of dimer 10 is formed (Scheme 6-6a). [Pd(PPh 3 ) 2 Cl 2 ] has the benefit of air and temperature stability and is less expensive than [Pd(PPh 3 ) 4 ], yet will always produce at least an equivalent amount of 10. Relevant examples of the Sonogashira crosscoupling with a variety of different compounds and conditions via these catalysts are shown in Table 6-1.…”

“…This enediyne functionality is commonly constructed using the Sonogashira protocol, which is elegantly exemplified in the construction of dynemicin A system 43 by Schreiber et al [95]. Intramolecular cross-coupling of 44 gave tricyclic intermediate 45, which sets the conjugated 1,3-diene up for a transannular Diels-Alder reaction with the trans-enoate moiety, providing 43 in one step (Scheme [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Three rings and four contiguous stereocenters are formed in this remarkable one-pot reaction.…”

“…Because of the discovery of simple and more efficient catalytic sp cross-coupling procedures, the Stephens-Castro reaction is not widely used today, but a few recent examples have been reported [7,[10][11][12][13]. One illustration is the synthesis of the anti-aromatic dehydrobenzo [12]annulene (DBA) 1 (Scheme 6-3) [12].…”

An Investigation into the Stephens–Castro Synthesis of Dehydrotriaryl[12]annulenes: Factors Influencing the Cyclotrimerization

“…P( t Bu) 3 and P( n Oct) 3 , 4) conducting the thermal cyclization step in non‐ or poor solvents for the ethynylcuprate e.g. p ‐xylene and 1‐methylmorpholine; 5) the presence of H 2 O in the thermal cyclization step; 6) reaction dilution; 7) heteroatoms adjacent to the coupling site, which may influence the thermal instability of the ethynylcuprate, and 8) the presence of structurally different ethynylcuprates such as intermediate 16 in the presence of 8 . Overall, the stoichiometric reactions were insensitive to the anion (chloride vs. iodide), the ethynylcuprate ageing time and duration of thermal cyclization, as long as sufficient time was afforded for both processes, and that the latter was conducted within the temperature window of 120–170 °C.…”

π‐Conjugated Macrocycles Bearing Angle‐Strained Alkynes

“…Representative examples are shown in Figure . Although thiophene‐fused dehydroannulene 147 (CCDC: 1205022) was confirmed by X‐ray analysis to be strain free, its derivatives 148 seem to be slightly strained. The X‐ray data (CCDC: 1119562, 148 b ) are not sufficient to discuss the bond angles of the alkynes.…”