A convenient procedure for the monosilylation of symmetric 1,n-diols

In this paper we describe the development of a fully-automated solution-phase synthesizer, 'ChemKonzert' that can be used to prepare a wide variety of organic compounds. The automated synthesizer is ingeniously designed to perform most of the chemical reactions currently used by synthetic organic chemists and utilizes a centrifugal separator to efficiently achieve liquid-liquid extraction. The design of the hardware and software will be described in this paper, and several examples of organic reactions will also be presented as applications of the apparatus.

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“…5. 9) In addition, the handling of NaH was shown, including the ability to wash the reagent with dry hexane before use, in order to clean it.…”

Section: Resultsmentioning

confidence: 99%

Development and Application of a Solution-Phase Automated Synthesizer, 'ChemKonzert'

Machida¹,

Hirose²,

Fuse

et al. 2010

Chem. Pharm. Bull.

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“…H-Y, Na-Y were purchased from TOSOH Co. SiO 2 (230-400 mesh) was purchased from Merck Co. Amberlite IR-120B and IRC-50 were purchased from Organo Co. All reactions were carried out under aerobic conditions. Compounds 4a, 4c, 4d are commercially available, and 4b, 19) 7, 20) 10, 21) 13, 22) 16 23) are known compounds. 29 Si MAS NMR spectra were measured at 59.6 MHz on a JNM-CMX 300 (JEOL) solid state NMR spectrometer equipped with a magic angle spin probe.…”

Section: Methodsmentioning

confidence: 99%

Deprotection of a Silyl Group with Mesoporous Silica

Itoh

Kodama

Yoshio

2007

CHEMICAL & PHARMACEUTICAL BULLETIN

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The silyl group has been widely used in organic synthesis as a typical hydroxyl protecting group. Especially, the triethylsilyl (TES) group and t-butyldimethylsilyl (TBDMS) group have been used for synthesis of natural products by many researchers since they are comparatively stable against acids and are easy to handle. 1) Although, in general, deprotection of these groups is carried out with acids or fluorine anion, the work-up to remove the acids, especially on a large scale, is tedious and the fluorine anion tends to give rise to side reactions due to its strong basicity. With this background in mind, recently, reaction fields for achieving environmentally benign processes have been designed by many researchers in synthetic organic chemistry.2) Easy work-up is an important factor for achieving an environmentally benign process and the use of heterogeneous catalysts is advantageous. Among them, mesoporous silicas, which possess uniform meso pores, of which pore sizes are 2-50 nm, 3) and narrow pore-distribution and high surface area against amorphous mesoporous materials, such as silica gel or alumina, have been paid much attention due to their potential utility as new heterogeneous catalysts and in providing shape selectivity. In the course of our study on the utility of mesoporous silicas in organic synthesis as solid acid, we have found that their use is feasible for deprotection of silyl groups, and, especially, MCM-41, 4,5) a typical mesoporous silica enables us to deprotect the TES group selectively from the TBDMS group. Selective deprotection of silyl groups can be performed with a variety of liquid protonic and Lewis acids 6-9) ; however, the work-up to remove the acids is tedious as mentioned above. On the other hand, the heterogeneous system is facile from the viewpoint of convenience of the work-up in which mesoporous silicas can be removed by only filtration, and, furthermore, mesoporous silicas have the possibility of recycling. In this paper, we report our detailed study on the scope and limitation of using mesoporous silicas for deprotection of silyl groups. Table 1 shows the results for the deprotection of several silyl ethers (1) of dodecanol with MCM-41 in MeOH. The trimethylsilyl (TMS) and TES ethers (1a, b) were completely deprotected to dodecanol (2); however, the TBDMS and triisopropylsilyl (TIPS) ethers (1c, d) were intact during the indicated reaction time. These results show that selective deprotection of the TES group from the TBDMS group is feasible with the MCM-41/MeOH system. Table 2 shows the results of selective deprotection of the TES group under several conditions by using a typical solid catalyst and TES and TBDMS ether of 1,4-butanediol (3a) as test substrate. In THF, the starting material (3a) was almost intact after stirring for 4 h (entry 1). When acetnitrile, acetone, water, and ethanol were used as a solvent, reactions were sluggish (entries 2-5). On the other hand, methanol was the solvent of choice, and mono-TBDMS ether of 1,4-butanediol (4a) was obtained in 83% yield ...

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“…More recently some other cyclic and acyclic heteroatomsubstituted dienes have shown a similar proclivity (7).3 However, some cyclic, purely hydrocarbon, diene molecules give cycloaddition products that arise predominantly by addition to the sterically more hindered face, and this has been rationalized as a result of mixing of framework u orbitals into the diene T system (11). Previously we synthesized the plane-nonsymmetrical diene 1, and we used the results of its reactions with various dienophiles to shed light on the transition state geometry of the Diels-Alder reaction (12).…”

Section: Introductionmentioning

confidence: 92%

π-Facial stereoselectivity in the Diels–Alder reactions of a rigid carbocyclic diene: spiro(bicyclo[2.2.1]heptane-2,1′-[2,4]cyclopentadiene)

Burnell¹,

Valenta²

1991

Can. J. Chem.

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A convenient procedure for the monosilylation of symmetric 1,n-diols

Abstract: Bifunctional reagents are important synthons for the organic chemist. Many of these reagents (3) have as their

Cited by 266 publications

References 2 publications

Development and Application of a Solution-Phase Automated Synthesizer, 'ChemKonzert'

Development and Application of a Solution-Phase Automated Synthesizer, 'ChemKonzert'

Deprotection of a Silyl Group with Mesoporous Silica

π-Facial stereoselectivity in the Diels–Alder reactions of a rigid carbocyclic diene: spiro(bicyclo[2.2.1]heptane-2,1′-[2,4]cyclopentadiene)

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