Palladium-Catalyzed Annulation of 2,2′-Diiodobiphenyls with Alkynes: Synthesis and Applications of Phenanthrenes

Abstract

A range of phenanthrene derivatives were efficiently synthesized by the palladium-catalyzed annulation of 2,2'-diiodobiphenyls with alkynes. The scope, limitations and regioselectivity of the reaction were investigated. The described method was adopted to synthesize 9,10-dialkylphenanthrenes, sterically overcrowded 4,5-disubstituted phenanthrenes and phenanthrene-based alkaloids. Reactions of highly methoxy-substituted biphenyls with 2-(2-propynyl)pyrrolidine and 2-(2-propynyl)piperidine gave 2-(9-phenanthylmethyl)pyrrolidines and 2-(9-phenanthylmethyl)piperidines, respectively. The products were transformed to phenanthroindolizidine and phenanthroquinolizidine alkaloids by the Pictet-Spengler reaction.

Synthesis, Structural Analysis, and Properties of [8]Circulenes

“…Tetraphenylene should be an ideal starting material, because the target molecule could be accessed by annulation of each "bay region" with a C 2 building block, thus forming a phenanthrenyl moiety from a biphenyl moiety. We pre-viously summarized synthetic methods for the preparation of phenanthrene, [15] and the most effective protocol is the palladium-catalyzed annulation of a 2-iodobiphenyl with an alkyne. [16] Scheme 1 shows the synthetic method toward substituted [8]circulenes.…”

Conversion of 2‐Iodobiaryls into 2,2′‐Diiodobiaryls via Oxidation‐Iodination Sequences: A Versatile Route to Ladder‐Type Heterofluorenes

“…As imilar Cu-catalyzed method using selenium and (N-methyl-2-pyrrolidone) (NMP) instead of sulfur and DMF [18a] allowed conversion of 6b and 9 into benzo [1,2- (15). [27] Atwofold iodine-lithium exchange/electrophilic trapping sequence proved effective for the preparation of germanium-and phosphoryl-bridged p-teraryls 12 and 13, [15a, 28] respectively.T he latter product was obtained as as eparable mixture of syn-a nd anti-isomers.B esides the heteroatom-bridged p-teraryls,t he Pd-catalyzed reaction of 6b with 5-decyne,u sing Wus conditions, [29] resulted in atwofold annulation to afford benzo[k]tetraphene derivative 14.Single-crystal X-ray diffraction analysis was performed for all of these ladder-type products except anti-13,w hich invariably demonstrated high levels of coplanarity of their Scheme 3. a) Conversiono f2',5'-diiodo-p-terphenyl derivatives 4a-4d to 2,2',2'',5'-tetraiodo-p-terphenyl derivatives 6a-6d,a nd b) conversion of 2,5-bis(2-iodophenyl)thiophene 7 to 3,4-diiodo-2,5-bis(2-iodophenyl)thiophene 9.Reaction conditions: i) mCPBA (3 equiv), TfOH (6 equiv), CH 2 Cl 2 ,RT, 2h;i i) CuI (20 mol %), L1 (40 mol %), [(nBu) 4 N]I (4 equiv), MeCN, 60 8 8C, 24 h. Inset:O RTEP drawing of 5b (thermal ellipsoids set at 50 %p robability), whereby hydrogen atoms, counteranions, and solvent molecules were omitted for clarity. [27] Atwofold iodine-lithium exchange/electrophilic trapping sequence proved effective for the preparation of germanium-and phosphoryl-bridged p-teraryls 12 and 13, [15a, 28] respectively.T he latter product was obtained as as eparable mixture of syn-a nd anti-isomers.B esides the heteroatom-bridged p-teraryls,t he Pd-catalyzed reaction of 6b with 5-decyne,u sing Wus conditions, [29] resulted in atwofold annulation to afford benzo[k]tetraphene derivative 14.Single-crystal X-ray diffraction analysis was performed for all of these ladder-type products except anti-13,w hich invariably demonstrated high levels of coplanarity of their Scheme 3. a) Conversiono f2',5'-diiodo-p-terphenyl derivatives 4a-4d to 2,2',2'',5'-tetraiodo-p-terphenyl derivatives 6a-6d,a nd b) conversion of 2,5-bis(2-iodophenyl)thiophene 7 to 3,4-diiodo-2,5-bis(2-iodophenyl)thiophene 9.Reaction conditions: i) mCPBA (3 equiv), TfOH (6 equiv), CH 2 Cl 2 ,RT, 2h;i i) CuI (20 mol %), L1 (40 mol %), [(nBu) 4 N]I (4 equiv), MeCN, 60 8 8C, 24 h. Inset:O RTEP drawing of 5b (thermal ellipsoids set at 50 %p robability), whereby hydrogen atoms, counteranions, and solvent molecules were omitted for clarity.…”

Metal‐Catalyzed Cascade Reactions: Useful Synthetic Tools for the Preparation of Polycyclic Arenes

“…These phenanthrene‐based alkaloids have strong biological properties, particularly antitumor activities . Although many synthetic approaches for preparing these alkaloids have been developed, a general protocol via suitable phenanthrene derivatives proved most effective …”

“…A range of phenanthrene derivatives 7 , including 9,10‐dialkylphenanthrenes and sterically overcrowded 4,5‐disubstituted phenanthrenes, were efficiently obtained by palladium‐catalyzed annulation of 2,2′‐diiodobiphenyls 6 with alkynes (Scheme ) . A putative mechanism for generating phenanthrene 7 starts with a Pd(0) species, which is formed by the reaction between p ‐xylene and Pd(OAc) 2 .…”