Thieno benzopyrans

Benzopyran 160 reacts with 2,3-dichloro-l, 4-naphthoquinone by substitution of both chlorine atoms. The unstable primary adduct 161 undergoes ring expansion of oxirane 162 to produce thieno benzoxipine 163 in 70% yield (Scheme 32 (1994JCS(P1)2191)). 

Figure 3.20. Visible spectrum of open form of 2-(2,4-dimethoxyphenyl)-2-(4-methoxyphenyl)-2//-benzo(fe)thieno[3,2- h -1 -benzopyran.

Treatment of 7-mercaptocoumarin 390 with MeSOsH affords 2/7-thieno[2,3-, ]-l-benzopyran-2-one 391. In contrast, isomeric benzopyran-2-one 392 is prepared from 390 under basic conditions (Scheme 65) <1998JHC847>. 

The use of hydroxy derivatives of five-membered benzo-fused heterocycles in place of naphthols in both the Iwai-Ide and Ti(OEt)4 syntheses of benzopyrans leads to hetero-fused 2//-[l]benzopyrans. Initial details of the formation and properties of the furo-, thieno- and their benzologues and indolo-fused benzopyrans appeared in the patent literature <95WOP05382, 96USP5527911>. 

A 5-methyl group, introduced to direct the chromenylation reaction to give the angular thieno[2,3-/ [l]benzopyran 22, R = Me, brings about red shifts of the order of 10 nm of both absorption bands and a small increase in colourability <03T2567>. 

Hetero-/-fused derivatives of indeno[/i]benzopyrans result from the chromenylation of fluoreno[3,4-()][l]benzofuranols and related S andNMe analogues. The furo- 25 and thieno-26 [2,3-7]benzopyrans show absorption bands between 450 - 530 nm and 550 - 640 nm according to the substituents on the gem diaryl function and generally appear as various shades of brown. The half-lives vary between 1 and 6 minutes, with the thiophene analogues exhibiting faster fade rates than the furan derivatives. The closed form of the sole pyrano-... 

The furo[2,3-/ ]benzopyran 34 system is more bathochromic than the more aromatic thieno (30, 31) and benzothieno (32) analogues and is also the fastest fading derivative <00MCLC(344)229>. 

Spiro [2H-l-benzopyran-2,2 -benzothiazolines] spiro [pyrroli din-3,1 -(py rro-lidino-[3,4-c]pyrrolidones)] sydnones thiadiazines thiadi azoles thiaoxaborepanes thiazaphospholanes thiazolo[3,2-a]benzimidazoles thiazolo[3,4-a]benzimidazoles thiazolo[3,2-a][l,3]diazepines thiazolo[2,3-b]quinazolines thieno[2,3-e][l,4]diazepines thieno[2,3-d]pyrimidines... 

Nyiondi-Bonguen E, Fondjo ES, Fomum ZT, Doepp D (1994) Condensation reactions of 3-amino-4-imino-4/f-thieno[3,4-c][l]benzopyran. J Chem Soc Perkin Trans 1 2191-2196... 

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