{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,25]],"date-time":"2025-10-25T18:39:16Z","timestamp":1761417556949},"reference-count":14,"publisher":"Elsevier BV","issue":"12","license":[{"start":{"date-parts":[[2002,3,1]],"date-time":"2002-03-01T00:00:00Z","timestamp":1014940800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/www.elsevier.com\/tdm\/userlicense\/1.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Tetrahedron Letters"],"published-print":{"date-parts":[[2002,3]]},"DOI":"10.1016\/s0040-4039(02)00234-4","type":"journal-article","created":{"date-parts":[[2003,3,25]],"date-time":"2003-03-25T20:14:42Z","timestamp":1048623282000},"page":"2203-2205","source":"Crossref","is-referenced-by-count":16,"title":["First report of a permanent open form of a naphthopyran"],"prefix":"10.1016","volume":"43","author":[{"given":"Cristina I.","family":"Martins","sequence":"first","affiliation":[]},{"given":"Paulo J.","family":"Coelho","sequence":"additional","affiliation":[]},{"given":"Luis M.","family":"Carvalho","sequence":"additional","affiliation":[]},{"given":"Ana M.F.","family":"Oliveira-Campos","sequence":"additional","affiliation":[]}],"member":"78","reference":[{"key":"10.1016\/S0040-4039(02)00234-4_BIB1","unstructured":"Van Gemert, B. In Organic Photochromic and Thermochromic Compounds; Crano, J. C.; Guglielmetti, R. J., Eds.; Plenum Publishing Corporation: New York, 1999; Vol. 1, Chapter 3."},{"key":"10.1016\/S0040-4039(02)00234-4_BIB2","unstructured":"Ichimura, K. Photochromism: Molecules and Systems; D\u00fcrr, H.; Bouas-Laurent, H., Eds.; Elsevier: Amsterdam, 1990; Chapter 26."},{"key":"10.1016\/S0040-4039(02)00234-4_BIB3","unstructured":"Laarhoven, W. H. Photochromism: Molecules and Systems; D\u00fcrr, H.; Bouas-Laurent, H., Eds.; Elsevier: Amsterdam, 1990; Chapter 7."},{"key":"10.1016\/S0040-4039(02)00234-4_BIB4","doi-asserted-by":"crossref","first-page":"1499","DOI":"10.1039\/a700612h","author":"Delbaere","year":"1997","journal-title":"J. Chem. Soc., Perkin Trans. 2"},{"key":"10.1016\/S0040-4039(02)00234-4_BIB5","doi-asserted-by":"crossref","first-page":"1153","DOI":"10.1039\/a800906f","author":"Delbaere","year":"1998","journal-title":"J. Chem. 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Soc., Perkin Trans. 2"},{"key":"10.1016\/S0040-4039(02)00234-4_BIB11","doi-asserted-by":"crossref","first-page":"3010","DOI":"10.1021\/ja00902a031","volume":"85","author":"Bender","year":"1963","journal-title":"J. Am. Chem. Soc."},{"key":"10.1016\/S0040-4039(02)00234-4_BIB12","unstructured":"Procedure for the synthesis of 2: To a mixture of 1,8-dihydroxynaphthalene 1 (201 mg, 1.26 mmol), 1,1-diphenylprop-2-yn-1-ol (563 mg, 2.70 mmol), PPTS (20 mg) and 60 ml of dry toluene were added. The suspension was refluxed for 2 h under an argon atmosphere. The toluene was evaporated under reduced pressure and the red oil which was obtained was purified by silica gel column chromatography (CH2Cl2\/hexane 20\u201360%). Recrystallisation from methanol gave a crystalline material: 285 mg, 65%; mp 146\u2013148\u00b0C; IR: 3409, 3029, 2870, 1724, 1625, 1550, 1440, 1241; 1H NMR (300 MHz, CDCl3) \u03b4 13.24 (s, 1H, OH), 8.10 (d, 1H, J=7.7 Hz), 7.78 (d, 1H, J=8.0 Hz), 7.53 (d, 1H, J=9.0 Hz), 7.51 (m, 2H), 7.42\u20137.31 (m, 9H), 7.11 (d, 1H, J=7.5 Hz), 6.93 (d, 1H, J=7.8 Hz), 6.57 (d, 1H, J=8.0 Hz), 13C NMR: 190.05, 162.52, 153.35, 141.51, 138.54, 137.14, 136.64, 134.07, 131.07, 129.39, 129.02, 128.59, 128.46, 126.33, 122.35, 116.25, 112.82; MS-EI m\/z 167 (12), 191 (20), 231 (12), 237 (17), 350 (M+, 100). Exact mass for C25H18O2: 350.130680; found 350.130595."},{"key":"10.1016\/S0040-4039(02)00234-4_BIB13","unstructured":"1H NMR (300 MHz) spectrum of the red dye 2 in CH3OD: \u03b4 8.41 (d, J=10 Hz, 1H), 7.81 (d, J=8 Hz, 1H), 7.76 (d, J=8 Hz, 1H), 7.60\u20137.30 (m, 11H), 7.30 (d, J=8 Hz, 1H), 6.90 (d, J=7.5 Hz, 1H), 6.58 (d, J=10 Hz, 1H); in CH3OD+NaOD: \u03b4 7.40 (m, 2H), 7.30\u20137.16 (m, 10H), 7.04 (t, J=8 Hz, 1H), 6.86 (d, J=8 Hz, 1H), 6.49 (d, J=8 Hz, 1H), 6.41 (d, J=8 Hz, 1H), 6.39 (d, J=8 Hz, 1H)."},{"key":"10.1016\/S0040-4039(02)00234-4_BIB14","doi-asserted-by":"crossref","first-page":"571","DOI":"10.1039\/p29880000571","author":"Hilbert","year":"1988","journal-title":"J. Chem. 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