“…2 Furthermore, 2 H -chromenes find interesting applications as photochromic materials and in the synthesis of dyes. 3 As a result, considerable efforts have been made for their synthesis over the past decades. 4, 5 Synthetic methods developed so far include Pd-catalyzed ring-closure of 2-isoprenyl phenols, 5a Claisen-rearrangement of propargyl phenol ethers, 5b Ru-catalyzed ring-closing methathesis protocols, 5c–f nucleophilic substitution of chromene acetals (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Metalloradical Approach to 2H-Chromenes

et al. 2014

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Cobalt(III)–carbene radicals, generated through metalloradical activation of salicyl N-tosylhydrazones by cobalt(II) complexes of porphyrins, readily undergo radical addition to terminal alkynes to produce salicyl-vinyl radical intermediates. Subsequent hydrogen atom transfer (HAT) from the hydroxy group of the salicyl-moiety to the vinyl-radical leads to the formation of 2H-chromenes. The Co(II)-catalyzed process can tolerate various substitution patterns and produces the corresponding 2H-chromene products in good isolated yields. EPR spectroscopy and radical-trapping experiments with TEMPO are in agreement with the proposed radical mechanism. DFT calculations reveal the formation of the salicyl-vinyl radical intermediate by a metalloradical mediated process. Unexpectedly, subsequent HAT from the hydroxy moiety to the vinyl radical leads to formation of an o-quinone methide intermediate, which dissociates spontaneously from the cobalt center and easily undergoes an endo-cyclic, sigmatropic ring-closing reaction to form the final 2H-chromene product.

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“…The naphalene-based to-sylhydrazone 1i gave access to 2 H -chromene 3t (Table 3, entry 8), which is of interest in the field of photochromic materials (see also Figure 1). 3 …”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metalloradical Approach to 2H-Chromenes

et al. 2014

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“…The slight decrease in DE 1 with extended UV exposure, more pronounced with dye 2, is likely to be associated with experimental difficulties in controlling the tendency of the prints to rise marginally in temperature with prolonged exposure under the UV lamp, which will accelerate the thermal reverse reaction, leading to a reduction in colour strength. It has been reported previously that the photochromism of spironaphthoxazines, such as dye 2, is more sensitive to temperature than that of naphthopyrans such as 6 [9,14]. On the basis of this observation, a UV exposure time of 4 min was used for subsequent studies.…”

Section: Resultsmentioning

confidence: 99%

Textile applications of photochromic dyes. Part 4: application of commercial photochromic dyes as disperse dyes to polyester by exhaust dyeing

Aldib

Christie

2011

Coloration Technology

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A series of commercial photochromic dyes was applied to polyester fabric as disperse dyes. The photocoloration properties of the dyed fabrics were investigated by applying techniques previously established in our laboratories using an independent source of ultraviolet irradiation and traditional colour measurement instrumentation. The dyed fabrics showed reversible photochromism, developing pronounced colours from weak background colours on irradiation with ultraviolet light and returning to their original state when the ultraviolet light source was removed. However, the extent of photocoloration and the depth of background colour varied significantly with the particular dye used. The dyeing procedure was optimised by maximising the degree of photocoloration, expressed as the colour difference (DE 1 ) between the colour developed after ultraviolet exposure and background colour, while minimising the background colour, expressed as the colour difference (DE 2 ) between unexposed dyed and undyed fabrics. Optimum dyeing concentrations were determined. The colour development and fading properties, fatigue resistance and storage stability of the dyed fabrics were investigated.

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“…Although fulgides have been used in conventional coloration areas such as textiles and printing inks [92], they are of more interest for functional applications [93].…”

Section: Fulgidesmentioning

confidence: 99%

Industrial organic photochromic dyes

Corns¹,

Partington²,

Towns³

2009

Coloration Technology

179

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Organic photochromic molecules are well established as colorants in the manufacture of niche products, providing striking colour change effects when irradiated with light. This paper describes the industrially important classes of photochromic dye in terms of their development and chemistries, the applications in which their photochromism is employed commercially, and the technical features behind their success. Photochromic systems form the subject of much industrially funded research into nascent high‐tech applications that have the potential to become the most commercially significant outlets for photochromic dyes. Those types being scrutinised are therefore also discussed along with the directions in which the industrial use of photochromic colorants may take.

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Cited by 54 publications

References 0 publications

Metalloradical Approach to 2H-Chromenes

Metalloradical Approach to 2H-Chromenes

Textile applications of photochromic dyes. Part 4: application of commercial photochromic dyes as disperse dyes to polyester by exhaust dyeing

Industrial organic photochromic dyes

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