A Facile Cascade Synthesis of 5,6-Diaryldibenzo[a,e]cyclooctenes from (Z,Z)-1-Aryl-3,5-octadiene-1,7-diynes

Abstract

Sequential treatment of (Z)-3-methyl-2-penten-4-ynal (10) with the allenylborane 2 and 2-aminoethanol furnished 11. The use of 11 for cross-coupling with aryl iodides followed by the KH-induced syn elimination of the coupled adducts 13 provided easy access to a variety of dienediynes 14 for subsequent conversions to dibenzo[a,e]cyclooctenes (sym-dibenzocyclooctatetraenes) 17. By cross-coupling with 1,2- and 1,4-diiodobenzene, it was possible to obtain 19 and 25 having two dienediynyl moieties. It was anticipated that the oligomers 21 and 26 containing multiple dibenzo[a,e]cyclooctenyl units could thus be synthesized. The 1H NMR spectrum of 32 having three dibenzo[a,e]cyclooctenyl units indicates the presence of three diastereomers 32a−c in a random statistical distribution of 2:1:1. Similarly, the 1H NMR spectrum of 33 having two dibenzo[a,e]cyclooctenyl units exhibits signals that support the presence of two diastereomers 33a and 33b in a 1:1 ratio.

Tandem Oxidative Ring Expansion for Synthesis of Dibenzocyclooctaphenanthrenes

“…Polycyclic arene units with negative curvature are prevalent in various curved nanographenes and hypothetical toroidal carbon nanotubes, which have attracted increasing attention in the field of computation and synthetic chemistry as well as materials science in terms of their negatively curved structural features and electronic properties. , Embedding seven- or eight-membered carbon rings into the polycyclic aromatic hydrocarbon (PAH) frameworks has been regarded as an intriguing strategy for the construction of the negatively curved polycyclic arenes . Particularly, polycyclic arenes fused with an eight-membered cyclooctatetraene (COT) and benzenoid rings, such as tetraphenylene, dibenzo­[ a , e ]­[8]­annulene (dbCOT), tribenzo­[ a , c , e ]­[8]­annulene (tribCOT), and dibenzo­[3,4:7,8]­cyclo­octa­[1,2- l ]­phenanthrene (dbCOTP), displayed negatively bent structures owing to the tub-shaped geometry of COT (Scheme a). They not only can serve as important key segments of negatively curved nanographenes − and Mackay crystals but also can act as COT ligands for transition metal complexes and host molecules for dynamic molecular recognition .…”

Synthesis of benzocarbazoles, indoloquinolines and indolonaphthridines from thermolysis of benzoenynyl ketenimines and carbodiimides

“…Calcd for C 22 H 17 N: C,89.46;H,5.80;N,4.74. Found: C,89.26;H,5.79;N,4.73. Preparation of 106d and 109d by the dehydration method was carried out by using the same procedure described for 106a except that a mixture of 0.706 g of 112d (2.00 mmol), 3.…”

“…Calcd for C 25 H 23 N: C,88.98;H,6.87;N,4.15. Found: C,88.78;H,6.82;N,4. 99, 137.39, 137.05, 133.87, 130.99, 130.83, 129.22, 127.70, 126.88, 126.67, 125.00, 124.81, 124.15, 123.61, 122.61, 122.39, 119.44, 116.29, 110.05, 31.37, 23.18, 14.80 13 C δ 141.84, 137.64, 136.76, 130.74, 130.64, 129.22, 128.75, 128.61, 127.81, 127.34, 125.16, 124.96, 124.44, 123.35, 122.63, 121.15, 119.44, 118.32, 118.10, 110.22 17, 141.79, 138.44, 137.08, 131.46, 131.00, 129.27, 128.68, 127.77, 127.32, 127.07, 126.33, 124.60, 124.12, 124.06, 123.66, 120.07, 118.31, 116.93, 109.93, 38.55, 33.63 (1 H, tm, J = 7.9 and 1.1 Hz), 0.78 (9 H, s); 13 C δ 142.27, 137.01, 136.82, 133.31, 132.29. 58 131.40, 130.77, 130.20, 129.53, 129.27, 127.92, 126.92, 126.53, 124.89, 124.53, 123.81, 121.67, 119.73, 118.33, 110.06, 3.47; MS m/z 365 (M + ), 350.…”

“…9,10 As for as enediyne cyclization, in 1971, Masamune et al reported the conversion of the two cyclic enediynes (7 and 10) into the corresponding benzenoid systems (9 and 12), but they did not mention the involvement of a biradical intermediate in the process (Scheme 1). 11 It was in 1987 that the enediyne chemistry did arouse much interest in chemical community when two very potent naturally occurring antitumor antibiotics, calicheamicins (1) and esperamicins (2) bearing an enediyne moiety, were discovered by researchers from the Lederle Laboratories 3 and Bristol-Myers 4 , respectively. In the proposed mechanisms for DNA cleavage by these enediyne antibiotics, the 1,4-benzenoid biradicals generated by the Bergman cyclization attack DNA deoxyribose by hydrogen atom abstraction (Scheme 3).…”

“…4 dynemicin 3, 5 C-1027 chromophore 4, 6 kedarcidin 5, 7 and neocarzinostatin (NCS) chromophore 6, 8 which cleave DNA via generation of biradicals under mild conditions(Figure 1). Among these thermally-induced biradical-forming reactions,…”