Structure and Photochemical Properties of r‐1, c‐2, t‐3, t‐4‐l, 3‐Bis [2‐ (5‐R‐benzoxazolyl) ] −2,4‐di (4‐R' ‐phenyl) cyclobutane

Abstract

molecule of IIc is centmsymmetric, which indicates that the dimerization process is a head-btail fahion. The selectivity of the photodimerization of Ia-Ic has been enhanced by using acidic solvent and the reaction speed would be decreased when electron donating gnxlp was introduced in the Qposition of the phenyl group. That the photodimerization is not affected by the presence of oxygen as well as its high stereo-selectivity demonstrated that the reaction proceeded through an excited singlet state. It was also found that under irradiation of short wavelength U V , these dimers underwent photolysis completely to reproduce its bnns-monomers, and then the new formed species changed into their ck-isomers through m -c k isomehtion.

Innovative Concept of Designing Primary Explosives by IntroducingPolymers: Preparation and Investigation of {[Ca(CHZ)2](ClO4)2}n (CHZ = carbohydrazide)

“…In general, sensitivity always accompanies low thermal stability in energetic materials. [26,[46][47][48][49] However, to our delight, the 1D polymer and multiple cyclic structures as well as the chelate rings of 1 stabilize the whole molecule, resolving the conflict. Further application properties, such as DDT length, minimum initiating charge, explosion heat, and C-J pressure will be measured in the near future and reported in following articles.…”

“…CHZ can react simultaneously with metal ions and oxidizing groups because of its strong reduction ability. Several metal carbohydrazido compounds, [17,18,[23][24][25] such as cadmium tri-(carbohydrazide) perchlorate and zinc tri(carbohydrazide) perchlorate, [26] have been successfully prepared and proved to be remarkable in practical applications. At the same time, researchers have also paid attention to energetic materials based on alkaline-earth metals.…”

Photochemistry of Cyclobutanes: Synthesis and Reactivity

“…Thus the daylight or UV irradiation of 32 in ethanol brings about dimerization and the formation of the cyclobutane 33 33 . The photochemical dimerization of the trans-1-[2-(5-R-benzoxazolyl)]-2-(4-Rphenyl)ethenes (R = H, Me, R = H, OMe) affords cyclobutane derivatives by head-to-tail dimerization 34 .…”

“…Typical results for the selectivity observed are shown in Scheme 3 40 The environment within single crystals can also provide a situation where dimerization is the dominant reaction. Typical of this is the irradiation of stilbene 40, co-crystallized with bis-p-phenylene [34]crown-10, that yields the dimer 41 in 80% yield 41 . The co-crystals obtained from 1,8-naphthalenedicarboxylic acid and the trans-1,2-di(4-pyridyl)ethene 42 are arranged in such a manner that the two ethene units lie in close proximity.…”

Design of crystal packings of styrylheterocycles and [2+2] photocycloaddition reactions in their single crystals 6. Synthesis and crystal packings of neutral crown-containing and model styrylheterocycles

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15] This method of the construc tion of carbon-carbon bonds holds promise because of the relative ease of the synthesis (irradiation at a specified wavelength), the reversibility and, in some cases, high stereoselectivity of the photoreaction yielding only some of the theoretically possible cyclobutane isomers. The PCA reaction can occur in concentrated solutions and in the solid state, including the single crystals.…”