343:
97:-stilbenes in the absence of a hydrogen-trapping agent. Suitably substituted stilbenes may undergo irreversible, rearomatizing elimination or -shift processes in the absence of an oxidant. Aryl enynes, heteroatomic stilbene derivatives (e.g. amides), and substrates containing a single heteroatom in place of the stilbene double bond also undergo the reaction.
114:
Regardless of the presence or absence of an oxidant, the first step of the reaction is photochemical excitation of a stilbene or similar structure, leading to formation of a dihydrophenanthrene or similar intermediate. For stilbene and other chemicals containing a double-bond linker between the two
336:
In 2015, Li and Twieg reported a novel derivative of
Mallory type photocyclizations and named it as photocyclodehydrofluorination (PCDHF). In the cyclization a stilbene (or ortho-terphenyl) with a pentafluorophenyl group, the fluorine atom can be used as a facile leaving group.
252:
carbons. Which carbon reacts depends on both steric and electronic factors. Electronically, the dihydrophenanthrene intermediate exhibiting greater aromatic stabilization is preferred. For instance, in 1-naphthyl-2-phenylethylene, electronic factors favor the formation of
358:-bromosuccinimide, transformation to the phosphonium salt, and a Wittig reaction with anaromatic aldehyde, photocyclization fuses the aromatic rings. Iteration of this sequence results in helicenes.
308:
Photocyclization can also form five-membered rings. In the vinyl naphthalene series, both oxidative and non-oxidative processes are possible; although the latter requires a proton-transfer catalyst.
187:-stilbene. However, suitably substituted stilbenes cyclize irreversibly if an aromatizing elimination or hydrogen shift process can take place. Examples of these transformations are provided below.
220:-Substituted substrates generally give 1-substituted phenanthrenes, unless the substituent is a good leaving group, in which case elimination to form unsubstituted phenanthrene occurs.
166:, the cyclized intermediate can be oxidized to aromatize the rings. For example, dihydrophenanthrene becomes phenanthrene. Oxygen and iodine are the most commonly employed oxidants.
630:
Mallory, F. B.; Mallory, C. W.; Halpern, E. J. First Middle
Atlantic Regional Meeting of the American Chemical Society, February 3, 1966, Philadelphia, Pa., Abstracts, p. 134.
375:
Several other methods are available to synthesize the phenanthrene ring system; however, most of these are longer or less functional group tolerant than photocyclization. The
280:
in the presence of an oxidant, such as iodine. Oxygen is unsatisfactory because ring-opening to highly stabilized terphenyl is faster than oxidation when oxygen is used.
154:
This cyclization is reversible, but several other subsequent reactions can occur instead, depending on structural details and whether certain other reagents are present.
320:
Cyclization of arylvinyl- or diarylamines provides indolines and carbazoles, respectively. In one interesting example, the use of circularly polarized light provided
236:
Substitution of the exocyclic double bond is well tolerated. Polycyclic aromatic compounds can be synthesized using substrates containing multiple aromatic rings.
354:
Photocyclization can be used as the final step of a sequence to generate a fused aromatic ring at a benzylic position. After benzylic bromization with
474:
330:
314:
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286:
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230:
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For most substrates, in the absence of an oxidant, the dihydrophenanthrene intermediate may reversibly open to the corresponding
393:
103:
59:
384:
816:
380:
136:
93:
to give polycyclic aromatics. Typically, the dihydrophenanthrenes themselves are relatively unstable, and revert to
67:
718:
826:
821:
470:
39:
248:
Stilbene derivatives containing fused aromatic systems may cyclize using either of two nonequivalent
43:
82:
746:
738:
140:
31:
795:
730:
455:
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17:
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symmetry analysis of the photochemical reaction of the six-electron system explains the
475:
Remembering the
Distinguished Career of Long-Time Professor of Chemistry Frank Mallory
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63:
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55:
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conformation about the C-O single bond, do not undergo this process efficiently.
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443:
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Amides may cyclize to form lactams. Esters, which exist primarily in the
224:- Substituted substrates give mixtures of 2- and 4-substituted products.
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51:
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301:
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241:
229:
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aromatic rings, the excited structure can undergo reversible
763:
Laarhoven, W. H.; Cuppen, Th. J. H. M.; Nivard, R. J. F.
503:
Thyagarajan, B. S.; Kharasch, N.; Lewis, H. B.; Wolf, W.
127:
structures can undergo the cyclization step themselves,
147:
relative configuration at the newly bound centers by a
276:-Terphenyl substrates cyclize to the corresponding
676:Lapouyade, R.; Koussini, R.; Bouas-Laurent, H.
70:, who discovered it while a graduate student.
8:
77:and its derivatives undergo intramolecular
596:Lapouyade, R.; Koussini, R.; Rayez, J.-C.
592:
590:
204:Photocyclization can be carried out with
717:Li, Zhe; Twieg, Robert J. (2015-09-11).
783:Floyd, A. J.; Dyke, S. F.; Ward, S. E.
404:
486:Tinnemans, A. H. A.; Laarhoven, W. H.
135:and then cyclize. In keeping with the
659:Ninomiya, I.; Naito, T.; Kiguchi, T.
613:Cava, M. P.; Stern, P.; Wakisaka, K.
7:
572:
570:
437:
435:
536:Cuppen, J. H. M.; Laarhoven, W. H.
216:-substituted stilbene substrates.
25:
639:Sato, T.; Shimada, S.; Hata, K.
556:Giles, R. G. F.; Sargent, M. V.
391:
362:
341:
328:
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300:
284:
265:
240:
228:
191:
170:
101:
60:polycyclic aromatic hydrocarbons
719:"Photocyclodehydrofluorination"
576:Sargent, M. V.; Timmons, C. J.
441:Mallory, F. B.; Mallory, C. W.
324:in slight enantiomeric excess.
723:Chemistry - A European Journal
661:J. Chem. Soc., Perkin Trans. 1
558:J. Chem. Soc., Perkin Trans. 1
488:J. Chem. Soc., Perkin Trans. 1
1:
123:isomerization. Although only
110:Mechanism and stereochemistry
696:Nicoud, J. F.; Kagan, H. B.
598:J. Chem. Soc., Chem. Commun.
520:Zeller, K.-P.; Petersen, H.
460:10.1002/0471264180.or030.01
387:are two such alternatives.
89:, the dihydrophenanthrenes
843:
62:and heteroaromatics. This
58:and other polycyclic form
131:structures can isomerize
27:Organic chemical reaction
18:Stilbene photocyclization
261:in a ratio of 98.5:1.5.
179:Non-oxidative conditions
85:. In the presence of an
473:. (November 16, 2017) "
428:10.1021/acs.joc.0c00924
137:Woodward–Hoffmann rules
735:10.1002/chem.201502473
578:J. Chem. Soc. Suppl. 1
350:Synthetic applications
162:In the presence of an
73:Under UV irradiation,
641:Bull. Chem. Soc. Jpn.
200:Scope and limitations
817:Pericyclic reactions
158:Oxidative conditions
83:dihydrophenanthrenes
800:10.1021/cr60303a001
729:(44): 15534–15539.
54:structures to form
678:J. Am. Chem. Soc.
538:J. Am. Chem. Soc.
141:molecular orbital
32:organic chemistry
16:(Redirected from
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164:oxidizing agent
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827:Name reactions
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822:Photochemistry
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46:reaction of di
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505:Chem. Commun.
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413:J. Org. Chem.
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278:triphenylenes
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68:Frank Mallory
66:is named for
65:
64:name reaction
61:
57:
56:phenanthrenes
53:
49:
45:
42:-cyclization–
41:
40:photochemical
37:
33:
19:
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471:Cassidy, Kim
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411:Lvov, A. G.
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765:Tetrahedron
615:Tetrahedron
444:Org. React.
149:conrotatory
79:cyclization
44:elimination
811:Categories
785:Chem. Rev.
400:References
743:0947-6539
522:Synthesis
151:process.
91:aromatize
751:26360126
379:and the
371:See also
81:to form
75:stilbene
52:ethylene
794:, 509.
774:, 3343.
687:, 7374.
667:, 2257.
650:, 2484.
584:, 5544.
564:, 2447.
547:, 5914.
494:, 1115.
212:-, and
133:in situ
87:oxidant
749:
741:
604:, 676.
527:, 532.
511:, 614.
383:-type
34:, the
707:, 78.
454:, 1.
294:trans
274:ortho
257:over
250:ortho
218:ortho
206:ortho
145:trans
129:trans
121:trans
38:is a
788:1976
768:1974
747:PMID
739:ISSN
701:1977
681:1977
665:1973
644:1971
602:1975
582:1964
562:1974
541:1972
525:1975
509:1967
492:1976
448:1984
416:2020
222:meta
214:para
210:meta
48:aryl
796:doi
731:doi
456:doi
424:doi
208:-,
185:cis
125:cis
117:cis
95:cis
30:In
813::
792:76
790:,
772:30
770:,
745:.
737:.
727:21
725:.
721:.
705:15
703:,
685:99
683:,
663:,
648:44
646:,
619:29
617:,
600:,
589:^
580:,
569:^
560:,
545:94
543:,
507:,
490:,
452:30
450:,
434:^
420:85
418:,
139:,
798::
753:.
733::
477:"
458::
426::
356:N
322:3
259:2
255:1
119:-
50:-
20:)
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