Rapid Regio- and Diastereoselective Paternò−Büchi Reaction of Alkyl Phenylglyoxylates

Hu, Shengkui; Neckers, Douglas C.

doi:10.1021/jo9615054

Cited by 50 publications

(24 citation statements)

References 22 publications

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“…2 It is held that the formation of a biradical following the interaction between a excited ketone and an alkene can occur from ketones having a n* character and not from those exhibiting a *. 12,18,21,22 As expected, however, Figure 2 shows that a linear relationship between E T and log k q is observed for the four monomers examined.…”

Section: Role Of the Value Of The Ketone Triplet Energysupporting

confidence: 78%

On the interaction mechanism of radical photoinitiators with monomers

Lemee¹,

Burget²,

Jacques³

et al. 2000

J. Polym. Sci. A Polym. Chem.

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Section: Role Of the Value Of The Ketone Triplet Energysupporting

confidence: 78%

On the interaction mechanism of radical photoinitiators with monomers

Lemee¹,

Burget²,

Jacques³

et al. 2000

J. Polym. Sci. A Polym. Chem.

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“…3) was found to be 7 ± 8 kcal/mol less stable than conformer A, which leads to the undesired fragmentation ( Table 3). A lower energy difference of 4.37 kcal/mol was also previously determined by Hu and Neckers with semi-empirical AM1 calculations [27].…”

Section: Photoirradiations Of A-keto Esters In Undegassed Solutions Asupporting

confidence: 76%

“…To elucidate its structure, small quantities of compound 29 were isolated as a diastereoisomeric mixture by preparative GC from a solution of 9 in MeCN, which was irradiated for 3 h with a Xe lamp. The 1 H-and 13 C-NMR spectra of the major isomer were found to be identical to those described by Hu and Neckers for an oxetane resulting from the intramolecular Paterno Á-Büchi reaction of 9 [27]. Two possible structures, namely 29a ± d and 30a ± d (Fig.…”

Section: Photoirradiations Of A-keto Esters In Undegassed Solutions Asupporting

confidence: 72%

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Controlled Release of Perfumery Aldehydes and Ketones by Norrish Type-II Photofragmentation of -Keto Esters in Undegassed Solution

Rochat

Minardi

Laumer

et al. 2000

HCA

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Alkyl or aryl a-keto esters of primary or secondary alcohols decompose upon irradiation at 350 ± 370 nm from the intermediate triplet state into aldehydes or ketones in polar, as well as apolar solvents. The use of these keto esters as delivery systems for the controlled release of perfumery aldehydes and ketones was investigated by photoirradiation in the presence of oxygen with a Xe or UV lamp, as well as outdoor sunlight. Systematic GC/ MS analysis of the irradiated solutions showed that, under these conditions, the desired Norrish type-II fragmentation of the ester side chain is the predominant reaction pathway in most of the cases. g-H Abstraction from the alkyl side chain of alkyl keto esters, as well as an intramolecular PaternoÁ-Büchi reaction or epoxidation of the alkene function in different citronellyl a-keto esters were identified as the most important side reactions. Some of the experimental findings have been rationalized on the basis of ab initio and density-functional calculations. (Cyclohexyl)oxoacetates and oxo(phenyl)acetates were found to be the most suitable precursors for the desired perfumery applications.1. Introduction. ± Aldehydes and ketones are important classes of fragrances that are present in all kinds of perfumes. However, many of them are very volatile and can, after application, only be perceived over a relatively short period of time. Furthermore, as constituents of perfumes for a variety of different bodycare or household applications, such as shampoos, soaps, all purpose cleaners, fabric softeners, or detergent powders, they are often too hydrophilic and thus easily carried away by water during various rinsing processes instead of staying on substrates like hair, skin, or fabrics.To prolong the desired odor perception of this class of compounds, we have prepared a series of photolabile, hydrophobic, non-volatile fragrance precursors as potential delivery systems for the controlled release of perfumery aldehydes and ketones in typical bodycare and household applications. In this publication, we describe the fragrance release from a-keto esters upon irradiation with artificial light sources, as well as natural sunlight in the presence of O 2 [1]. Some interesting fragrances for release in functional perfumery are depicted in Fig. 1 [2].The photolysis of alkyl or aryl a-keto esters of primary or secondary alcohols has been intensively studied since the early sixties [3 ± 7]. It was found that these esters decompose from their intermediate triplet state into aldehydes or ketones upon irradiation at 350 ± 370 nm in polar, as well as apolar solvents [7 ± 11]. Most of the photoirradiations described in the literature were carried out in degassed solutions in the absence of O 2 . The relatively good yields of the fragmentation process have allowed the use of a-keto esters as intermediates for the transformation of primary or secondary alcohols to aldehydes and ketones, respectively [12].

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“…The PB reaction of arylglyoxylates with furan was also found to produce stereoselectively the bicyclic oxetanes (Scheme 7.23) [41]. Neckers and coworker demonstrated the highly efficient formation of oxetanes in the intramolecular PB reaction (Scheme 7.24) [42]. It should be noted that the stereoselectivity is also completely different from that associated with triplet 1,4-biradicals.…”

Section: Stereoselective Syntheses Of Oxetanesmentioning

confidence: 99%

Formation of a Four‐Membered Ring: Oxetanes

Abe

2009

Handbook of Synthetic Photochemistry

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Oxetanes, four-membered cyclic ethers, have a ring strain energy (SE) of approximately 110 kJ mol À1 [1] and polar properties of the CO bonds (Figure 7.1). Thus, similar to the synthetic utility of oxiranes (epoxides, SE ¼ 114 kJ mol À1 ), the ringopening reaction of oxetanes, accompanying bond-formation reactions, would be very useful for synthetic purposes [2]. Since the oxetane ring is an important structural component of biologically active compounds, such as merrilactone A [3], thromboxane A2 [4], oxetanocin [5], oxetin [6], taxane alkaloids [7], and laureacetal-B [8], efficient and selective methods to synthesize the strained structure are currently active areas of research. Moreover, oxetane-ring-containing compounds are important industrial curing agents [9]. As a consequence, there are today over 2900 patents which include the term oxetane as a key word.All of these findings clearly indicate that the demand for synthetic oxetanes is high. There are basically three methods for preparing oxetanes:1. The intramolecular nucleophilic substitution reaction. 2. The ring-expansion reaction of epoxides. 3. The thermal and photochemical [2 þ 2] cycloaddition reaction of alkenes with carbonyls.The intramolecular nucleophilic substitution reaction -for example, the Williamson-type reaction -represents one of the important methods for preparing oxetane ring structures, and have been widely applied to the synthesis of oxetanes (Scheme 7.1) [10]. Unfortunately, side reactions -which include fragmentation from the intermediary alkoxide anion or elimination from the intermediary carbocation -often decrease the chemical yields of oxetane formation.The ring-expansion reaction of epoxides was first reported by Okuma and coworkers, to produce less-substituted oxetanes (Scheme 7.2) [11]. The nucleophilic attack by dimethyloxosulfonium methylide is proposed to react with the lessHandbook of Synthetic Photochemistry. Edited

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Rapid Regio- and Diastereoselective Paternò−Büchi Reaction of Alkyl Phenylglyoxylates

Cited by 50 publications

References 22 publications

On the interaction mechanism of radical photoinitiators with monomers

On the interaction mechanism of radical photoinitiators with monomers

Controlled Release of Perfumery Aldehydes and Ketones by Norrish Type-II Photofragmentation of -Keto Esters in Undegassed Solution

Formation of a Four‐Membered Ring: Oxetanes

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