Acylsilanes have been knownt ou ndergo isomerizationt os iloxycarbenesu nder photoirradiation and the thus generated carbenes can be utilized for various synthetic reactions. But this carbene formation is not necessarily efficient with some alkanoylsilanes because Norrishtype fragmentations compete, which limit the synthetic utility of alkanoylsilanes as carbene precursors. In this study,g eneration of siloxycarbenes from alkanoylsilanes by visible-light-inducedenergyt ransfer was examined by using an Ir complex, [Ir{dF(CF 3 )ppy} 2 (dtbpy)]PF 6 ,a nd was successfully applied to the CÀCc oupling reactions with boronic esters or aldehydes. This methodology efficiently suppressed undesired Norrish-type reactions and broadened synthetic utility of alkanoylsilanes.Photocatalytic organic transformations have attracted significant attention in currents ynthetic chemistry.P hotoredox process involving ar adicali ntermediate is gaining importance in this field. [1] Another interesting aspect of photocatalytic reactions is triplet energy transfer processes which enableg eneration of triplet-excited states of organic substrates through energy transfer from photoexcited catalysts. [1b,c,e, 2] From as ynthetic point of view,t riplete nergy transfer is considered to have some benefits [3] as compared to direct photoexcitation of organic substrates:i )highly energetic singlet-excited states of substrates, whichs ometimes induce undesired reactions, can be avoided, and ii)ite nables excitationo fs ubstrates with longer wavelength light than the inherent absorption band of substrates.It has been known that triplet-excited states of acylsilanes 1 undergo a1 ,2-silyl migration to generatet ransienta nd nucleo-philic siloxycarbene intermediates 2 (Scheme 1a). [4] Since Brook and co-workers originally discoveredt his photoisomerization through reaction of siloxycarbene intermediates 2 with polar compounds such as alcohols over fifty years ago, [5] various synthetic reactions utilizingp hotochemically generated siloxycarbenes 2 have been developed by several groups [6] including us. [7] However, in contrast to the reactions of aroylsilanes (1, R 1 = aryl), the use of alkanoylsilanes (1,R 1 = alkyl) has been quite limited. [8] We have already reported intermolecularc oupling reactions of photochemically generated siloxycarbenes 2 with boronic esterso raldehydes under neutral or Lewis acidic conditions (Scheme 1b). [7] Duringt he course of these studies, we noticed that serious undesired photochemical processes competed with siloxycarbene formation in the reactions with somea lkanoylsilanes.F or example, UV irradiation( 365 nm) of am ixture of 4-phenylbutanoylsilane 1a [9] and boronic ester 5 gave styrene along with the desired coupling product 3a in low yield (Scheme 2). The formation of styrene clearly indicated that Norrish type II fragmentation [10,11] competed with the desired photochemical isomerization to siloxycarbene 2 from excited stateso falkanoylsilane 1a.Scheme1.a) Photochemical generation of siloxycarbenes. b) Photoi...
In DPPC liposomes, the most prominent change was induced by PUFAs, whereas, in DPPC/Ch and DPPC/DOPC/Ch liposomes, OA had a stronger effect than PUFAs. The effect of PUFAs was strongly affected by the amount of Ch in the membrane, which confirmed a specific effect of PUFAs on the Ch-poor membrane domain. We further explored the effect of fatty acids dispersed in a water-in-oil-in-water multiple emulsion and found that unsaturated fatty acids acted on the membranes even when incorporated in emulsion form. These findings suggest that treatment with PUFAs increases the segregation of ordered and disordered phase domains in membranes.
Postherpetic neuralgia (PHN) is the most common complication following acute varicella zoster virus infection. PHN is associated with chronic severe pain and is resistant to conservative management treatments. The purpose of this study was to evaluate the effect of 0.3-millisecond multi-pulsed 1064-nm Nd:YAG laser treatment on PHN. Five subjects were treated with 2 - 3 sessions at 2-week interval. After the treatments, reduced visual analog scale (VAS) scores were noted in all patients. Treatments showed no adverse or intolerant effects and all patients felt warmth and comfort during the therapy. We first reported treating PHN patients using 0.3-millisecond multi-pulsed 1064-nm laser Nd:YAG. The results showed remarkable improvements in pain. This laser treatment could be an alternative choice for PHN patients with intractable neuralgia
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