- Total synthesis of (±)-cis-trikentrin B via intermolecular 6,7-indole aryne cycloaddition and Stille cross-coupling
-
An efficient total synthesis of the annulated indole natural product (±)-cis-trikentrin B was accomplished by means of a regioselectively generated 6,7-indole aryne cycloaddition via selective metal-halogen exchange from a 5,6,7-tribromoindole. The unaffected C-5 bromine was subsequently used for a Stille cross-coupling to install the butenyl side chain and complete the synthesis. This strategy provides rapid access into the trikentrins and the related herbindoles, and represents another application of this methodology to natural products total synthesis. The required 5,6,7-indole aryne precursor was prepared using the Leimgruber-Batcho indole synthesis.
- Chandrasoma, Nalin,Brown, Neil,Brassfield, Allen,Nerurkar, Alok,Suarez, Susana,Buszek, Keith R.
-
-
Read Online
- Trifluoromethanesulfonyloxy-group-directed regioselective (3 + 2) cycloadditions of benzynes for the synthesis of functionalized benzo-fused heterocycles
-
Highly regioselective (3 + 2) cycloadditions of (trifluoromethanesulfonyloxy)benzynes [(triflyloxy)benzynes] with 1,3-dipoles followed by cross-coupling reactions provided multisubstituted benzo-fused heterocycles. The triflyloxy group at the 3-position of benzynes, and even that at the remote 4-position, greatly affected the regiocontrol of the cycloaddition. These groups also served to install other substituents at their ipso-positions.
- Ikawa, Takashi,Kaneko, Hideki,Masuda, Shigeaki,Ishitsubo, Erika,Tokiwa, Hiroaki,Akai, Shuji
-
supporting information
p. 520 - 526
(2015/02/05)
-
- An improved method for the bromination of metalated haloarenes via lithium, zinc transmetalation: A convenient synthesis of 1,2-dibromoarenes
-
A facile protocol for the synthesis of 1,2-dibromoarenes is described. A standard ortho-lithiation/bromination procedure, when applied to bromoarenes, resulted in poor yields of the corresponding 1,2-dibromoarenes (13-62% yield). However, transmetalation
- Menzel, Karsten,Fisher, Ethan L.,DiMichele, Lisa,Frantz, Doug E.,Nelson, Todd D.,Kress, Michael H.
-
p. 2188 - 2191
(2007/10/03)
-
- Extensive halogen scrambling and buttressing effects encountered upon treatment of oligobromoarenes with bases
-
As a rule, tri-, tetra- and pentahaloarenes readily undergo ortho-lithiation when treated with amide-type bases. However, halogen migration occurs whenever the substrate contains three or more contiguous halogen atoms, provided that at least one of them is bromine or iodine. Dismutation and reduction processes often take place concomitantly. In this manner, a variety of organometallic intermediates may be formed, the driving force always being a decrease in basicity. When no such energy gain can be achieved, a sterically crowded substrate may just turn out to be inert; this was found to be the case with 1,5-dibromo-3-fluoro-2-(trimethylsilyl)benzene, 1,5-dibromo-3-fluoro-2,4-bis(trimethylsilyl)benzene, and 1,5-dibromo-3-fluoro-2,4-diiodobenzene. Buttressing effects are apparently strong enough to prevent expedient deprotonation of those substrates.
- Mongin, Florence,Marzi, Elena,Schlosser, Manfred
-
p. 2771 - 2777
(2007/10/03)
-
- Biphenylene dimer. Molecular fragment of a two-dimensional carbon net and double-stranded polymer
-
Biphenylene dimers, which may be considered as 'macrocyclic' 2 x 2 fragments of net 1 and dimeric fragments of a double-stranded polymer, 5, are prepared. X-ray crystallography on two polymorphs of the dimer 9 reveals that its bond alternation is analogous to that in biphenylene; the tetraphenylene part of 9 has approximately C(2h) symmetry with a small dihedral angle (.-,M+ (M = Li, K) and 92-,2M+ (M = Li, K), were generated and characterized by ESR, NMR, and UV-vis spectroscopies. The spectral data for the dianions are compatible with classical structures; no evidence for 'in-plane aromaticity' is found. For polymer 5, a localized band and large density of states near the Fermi level are found, using extended Huckel theory calculations.
- Rajca, Andrzej,Safronov, Andrej,Rajca, Suchada,Ross II, Charles R.,Stezowski, John J.
-
p. 7272 - 7279
(2007/10/03)
-
- Pyridine derived agents for cardiovascular diseases
-
STR1 Compounds of formula (I) or a biolabile ester thereof, or a pharmaceutically acceptable salt of either, wherein Rl, R2, R3 and R4 are each independently selected from H or C1 -C4 alkyl; R5 is (CH2)m SO2 R6, (CH2)m NHSO2 R6 or (CH2)m NHCOR7 ; R6 and R7 are C1 -C6 alkyl, C1 -C3 perfluoroalkyl(CH2)n, C3 -C6 cycloalkyl(CH2)n, aryl(CH2)n or heteroaryl(CH2)n ; or R6 is NR8 R9 ; R8 is H or C1 -C4 alkyl; R9 is C1 -C6 alkyl, C3 -C6 cycloalkyl(CH2)n, aryl(CH2)n or heteroaryl(CH2)n ; or R8 and R9 together with the nitrogen atom to which they are attached form a 5- to 7-membered heterocyclic ring which may optionally incorporate a carbon-carbon double bond or a further hetero atom linkage selected from O, S, NH, N(C1 -C4 alkyl) and N(C1 -C5 alkanoyl), and which may optionally be substituted with one to three substituents each independently selected from C1 -C4 alkyl and C1 -C4 alkoxy, and which may optionally be benzo-fused; X is CH2, CHCH3, C(OH)CH3, C=CH2 or O; m is 0 or 1; n is 0, 1, 2 or 3; and Het is 3- or 4-pyridyl or 1-imidazolyl; with the proviso that when Het is 1-imidazolyl then X is CH2 or CHCH3, are combined thromboxane A2 synthetase inhibitors and thromboxane A2 /endoperoxide antagonists of utility in the treatment of disease conditions in which thromboxane A2 is a causative agent.
- -
-
-
- Magnetic susceptibilities of organic compounds: Part V - Influence of substituents on diamagnetic susceptibilities of disubstituted and trisubstituted benzenes
-
The magnetic susceptibilities of a number of triads of isomeric disubstituted benzenes have been determined, choosing the compounds in such a way that the substituents are present in the following combinations: (i) two electron-releasing substituents, (ii) a halogeno and an electron-releasing substituent, (iii) a halogeno and an electron-attracting substituent, and (iv) two halogeno substituents.The data show that for types (i), (ii) and (iv), the ortho isomers have the highest magnetic susceptibilities, the susceptibilities decreasing in the order: ortho > meta > para; for type (iii), the meta-isomers have the highest susceptibilities, the susceptibilities decreasing in the order: meta > para > ortho.The diamagnetic susceptibilities of some isomeric trisubstituted benzenes have also been determined and the data reveal that the susceptibility is the highest where the crowding of substituents is the highest (1,2,3-isomer) and lowest where the substituents are staggered and least crowded (1,3,5-isomer).Another observation made in the case of trisubstituted benzene is the applicability of a principle of additivity of their diamagnetic susceptibilities.
- Baliah, V.,Jeyanthy, J. Judith Diana
-
p. 472 - 476
(2007/10/02)
-
- Process for producing 1,3,5-trichlorobenzene
-
1,3,5,-Trichlorobenzene is produced by chlorinating 1,3,5-trihalobenzene having 1 to 3 bromine atom and 2 to 0 chlorine atom. The gaseous 1,3,5-halobenzene having 1 to 3 bromine atom and 2 to 0 chlorine atom is brought into contact with chlorine gas at a molar ratio of 0.5 to 3.0 of the stoichiometric amount of chlorine required for said conversion, in a vapor phase at a temperature of 280° to 500° C.
- -
-
-