Substituent effects on the bridging modes of photochemical rearrangements of pyrazino-, quinoxalino-, and benzoquinoxalinobarrelenes

Substituent effects on the photorearrangements of unsymmetrically substituted diazinobarrelenes

“…Again, we face the same dilemma as to which of these bridging routes can account for the observed regioselectivity. From our previous report on the initial bridging patterns of deuterated quinoxalinobarrelene 2 9 and the dipropylsubstituted quinoxalinobarrelene 5 (R 1 = Pr; R 2 = H), 10 vinylvinyl bonding was favored. It appears that the same initial bridging pattern can be deduced for barrelenes 11 and 12.…”

“…In the case of pyrazinobarrelene 4b, we observed close to a 1 : 1 ratio of the photoproducts furnished via vinyl-vinyl and aryl-vinyl bridging; however, when the nitrile moiety was installed as in 4c only the photoproduct derived via aryl-vinyl bridging was observed. 10 This strongly suggests that the presence of the cyano group is indispensable for the preferred initial bridging. 22 Barrelenes 8 and 9 which have the nitrile groups attached at the pyrazine moiety may have exhibited similar regioselectivity for electron-withdrawing groups are known to lower triplet energies of aromatic compounds, 23 thus the triplet energy is heavily inclined on the aromatic ring.…”

“…The crude mixture was separated in a column (ethyl acetate : hexanes = 1 : 6) to obtain 35 (3.2 mg), and non-separable mixture of 32,33,2b,6b,4]pentaleno [1,2b]pyrazine-4,5-dicarbonitrile (35) IR (neat): 3058, 2922, 2854, 2236, 1732, 1626, 1539, 1371, 1332, 972, 836, 809 cm 21 ; 1 H NMR (400 MHz, CDCl 3 ) d 1.76 (d, J = 0.8 Hz, 3 H), 3.09 (ddd, J = 2.4, 6.0, 7.2 Hz, 1 H), 3.22 (dd, J = 6.0, 7.2 Hz, 1 H), 3.67 (ddd, J = 6.0, 6.0, 6.0 Hz, 1 H), 3.90 (d, J = 6.0 Hz, 1 H), 5.21 (m, 1 H); 13 C NMR (100 MHz, CDCl 3 ) d 13.2, 36.2, 41.9, 49.5, 56.3, 113.6, 113.8, 121.7, 129.2, 131.6, 143.9, 157.8, 162.6. MS (EI, 70 eV) m/z (%): 220 (57) [M + ], 219 (100), 206 (31), 71 (8), 63 (7), 57 (19), 55 (10); HRMS(EI) calcd for C 13 H 8 N 4 [M + ]: 220.0749, Found: 220.0770.…”

Efficient Synthesis and Subsequent Transformations of Phenylsulfanylbicyclo[2.2.2]octenones and Phenylselenylbicyclo[2.2.2]octenones

“…Our laboratory has succeeded in developing several strategies based on bicyclo[2.2.2]octenone derivatives and as a part of the effort to demonstrate the versatility of the developed strategies, these processes were utilized as key steps in the synthesis of cis -decalin natural products such as (±)-clerodane diterpenic acids, , (±)-eremopetasidione, (±)-3β-methacryloyloxyfuranoeremophilane, (±)-3β-angeloyloxyfuranoeremophilane, refuted (±)-bilosespenes A and B, triquinane-based natural products like (±)-magellanine and (±)-capnellene, and other natural products such as (±)-reserpine, (±)-forsythide aglucone dimethyl ester, (±)-annuionone, and (±)-tanarifuranonol . Another area of our interest is the photochemical rearrangements of highly substituted heteroarene-fused barrelenes . Compared to barrelenes and benzobarrelenes, heteroarene-fused barrelenes may have complicated reaction mechanisms due to the additional n,π* states. , In the context of studying the competitive aptitude of several possible reaction pathways in these reactions, easy access to bicyclo[2.2.2]octadienones were needed as suitable precursors for further manipulations to deliver the necessary heteroarene-fused barrelenes. , …”

Formation of a Three‐Membered Ring

“…The products 21a and 21b are generated via DPM and ADPM rearrangements, respectively. Recently, Liao and colleagues reported the details of substituent effects on the photochemical rearrangements of pyrazino-, quinoxalino-, and benzoquinolinobarrelenes [14].…”