Benzo-l,2:4,5-bis

The biradical benzo-l,2 4,5-bis(l,3,2-dithiazolyl) (BBDTA) is known in the literature but characterization is incomplete. A new study reports the electronic, molecular, and solid-state structure of BBDTA.224 The lifetime of an alkyl phenylglyoxalate-derived 1,4-biradical has been estimated, using the cyclopropylmethyl radical clock , to be in the range 35—40 ns.225 The indanols (88) and their C(3) methyl and trideuteromethyl analogues have been prepared from phenyl benzyl ketone via photo-cyclization of an intermediate 1,5-biradical species.226,227 Selectivity for these products over their C(l) epimers is high but is profoundly effected by substitution in the benzyl ring or the alkyl side-chain. The findings are rationalized in terms of the conformational preference of the intermediate 1,5-biradicals. 

Sodium-catalyzed condensation of l,2,4,5-tetrakis(chlorodiethylsilyl)benzene produced benzo[l,2 4,5]bis(l, 1,2,2-tetraethyl-l,2-disilacyclobut-3-ene) (Equation 29) <1998OM5830>. 

An W-formylated dibenzodiazocine was isolated in some cases in very poor yield <1998J(P1)1257>. Using the same synthetic approach, a series of fused diazocines were obtained. Thus, the action of bis-Vilsmeier reagents derived from W,W -dimethyl-W,W -diformyl-4-phenylenediamine with 4-substituted AUV-dimethylanilines, the diben-zo[ ]benzo[l,2-/4,5-/]bis-l,5-diazocines were obtained <2000S640>. Benzo[2,3]pyrido[6,7-A]-l,5-diazocines were synthesized from a Vilsmeier reagent derived from 4-W-(methylformamido)pyridine reacting with 4-substituted... 

The chemical shifts and coupling constants have been determined for the antifungal agent tjipanazole A (see Section 10.21.12) and a derivative <1998MI723>. NMR methods have been used to verify the formation of the radical cation in a benzo[l,2-[Pg.1141]

A series of benzo[l,2- 4,5- ]dichalcogenophenes (X= S, Se, Te) have been synthesized from l,4-dibromo-2,5-bis(2-trimethylsilylethynyl)benzene using a cyclization reaction between the acetylene substituents and the chalcogenate anion in good yield (Equation 94) <2005JOC10569>. 

Example 18 StiUe Cross-coupling Co-polymerization of 2,6-Bis(5-bromo-3-dode-cylthiophen-2-yl)benzo[l,2-[Pg.436]

Electron spin resonance (ESR) methods have been used to observe the formation of the radical cations and dications of benzoll,2- 4,5- ]bis[l,2,3]trithiole 13 and benzo[l,2-4 4,5- ]bis[l,2,3]dithiazole 17, and the experimental results confirm the ab initio calculations performed <2003EJ04902, 1997JA12136>. ESR has also been used to confirm the formation of superoxides upon photolysis of aryl benzobisthiazoles and aryl benzobisoxazoles in the presence of molecular oxygen <2003MM4699>. 

Synthesis of benzo[c]furans and isoindoles (181) is also possible by the addition of benzyne to the respective monocycles (178), followed by reduction (179 — 180) and pyrolysis. In an alternative procedure, (179) is reacted with 3,6-bis(2-pyridyl)-l,2,4,5-tetrazine, which affords (181) under far less vigorous conditions via a retro Diels-Alder reaction of the intermediate (182). 4-Phenyl-1,2,4-triazoles pyrolyze to form isoindoles (Section 3.4.3.12.2). 

Other syntheses of this type are exemplified by the conversion of 126 to 127 by treatment with sodium sulfide (Scheme 79) <2004T4361, CHEC-III(11.16.6.1.2)711 >, the synthesis of the tricyclic [l,2,4]triazolo[l,5-z][l,3]benzox-azine 129 by reaction of the triazolylphenol 128 with bis-trichloromethyl carbonate (Scheme 80) <1995JME2196, CHEC-III(11.16.6.1)710>, and the preparation of indolo[2,l-z]benzo[l,2,4]triazine derivatives 131 by diazotization of 2-amino- 1-aryltetrahydroindoles 130 followed by an intramolecular coupling of the diazonium group with the aryl moiety (Scheme 81) <2003H2519, CHEC-III(11.14.8.4)638>. 

If 1,5-difluoro-2,4-dinitrobenzene is used as the activated halogen compound, then in boiling DMF solution a double ring-closure to the tetraphenyl-17/,9//-benzo[l,2-c 5,4-e ]bi-s[l,3,4]thiadiazine (294) (14%) is noted. 2,4-Dinitrofluorobenzene also undergoes reaction with dithizone (PhN=NCSNHNHPh) in acetonitrile at 25 °C to yield 6-nitro-l-phenyl-3-phenylazo-l//-4,l,2-benzothiadiazine (293) as purple needles in 79% yield (see also Section 6.17.7.1.3). 

Polymers derived from benzo[l,2- i 5,4-heat-resistant polymers <86JAP(K)6128530>, electrophotographic toners <84JAP(K)5915256,83JAP(K)58176644) and liquid crystals for fibres and films... 

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