A mild and general synthesis of mixed orthoesters

Perron, F.; Gahman, Timothy C.; Albizati, Kim F.

doi:10.1016/s0040-4039(00)87824-7

Cited by 16 publications

(9 citation statements)

References 3 publications

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“…These orthoesters, known as “mixed orthoesters” are identified by a three alkoxy groups, of which two of them are usually structurally simple, and the third can be structurally complex. Selective access to these structures is quite limited, due to the difficulties associated with the standard methods which require use of TMOA with an acid catalyst, demanding long reaction time and purification. The latter seems a bit challenging, considering instability of the orthoesters towards silica gel.…”

Section: Carbon‐carbon and Carbon‐heteroatom Bond Formation Reactionsmentioning

confidence: 99%

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Orthoesters: Multiple Role Players in Organic Synthesis

Nazarian

Dabiri

2020

ChemistrySelect

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Dedicated to the memories of Prof. Abbas Shafiee Orthoesters are characterized by three alkoxy groups attached to a single carbon atom. This functional group is used primarily as a masking group for carboxylic acids, due to its robust stability towards strong nucleophiles and bases. Besides this protection role, orthoesters have further utility as versatile precursors in organic synthesis. This review focuses on the latter role of orthoesters as well as their applications in stereoselective synthesis.

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Section: Carbon‐carbon and Carbon‐heteroatom Bond Formation Reactionsmentioning

confidence: 99%

“…The latter seems a bit challenging, considering instability of the orthoesters towards silica gel. In a research paper published by Perron et al . the preparation of mixed orthoesters via reactions of alcohols with an excess amount of orthoesters was reported.…”

Section: Carbon‐carbon and Carbon‐heteroatom Bond Formation Reactionsmentioning

confidence: 99%

Orthoesters: Multiple Role Players in Organic Synthesis

Nazarian

Dabiri

2020

ChemistrySelect

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“…Albizati et al could demonstrate that the synthesis of mono-exchanged products can be achieved by reacting an alcohol with a large excess of an ortho ester in the presence of MgCl 2 . 2 This method has also been applied to the synthesis of a mixed ortho ester of a homoallyl alcohol. Using the substrates in almost equimolar amounts leads, of course, to mixtures of products derived from mono-, bis-and tris-exchange.…”

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confidence: 99%

Unexpected Lewis Acid Mediated Reactions of 1-Arylbut-3-en-1-ols with Trimethyl Orthoformate - A New Synthesis of Homoallyl Ethers and Chlorides

Merişor¹,

Conrad²,

Malakar³

et al. 2008

Synlett

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L e w i s A c i d M e d i a t e d T r a n s f o r m a t i o n o f 1 -A r y l b u t -3 -e n -1 -o l sAbstract: 1-Arylbut-3-en-1-ols react with trimethyl orthoformate in the presence of Lewis acids like InCl 3 , BiCl 3 , TiCl 4 , or BF 3 ·OEt 2 providing homoallyl ethers or homoallyl chlorides in high yields.Relatively little is known about reactions between ortho esters and alcohols. 1 Among the best known transformations of this kind is the acid-catalyzed transesterification of simple ortho esters with an excess of a less volatile alcohol. The resulting products are higher ortho esters with three identical OR groups. More difficult to achieve is the selective access to mixed ortho esters as no general preparation method is known. Albizati et al. could demonstrate that the synthesis of mono-exchanged products can be achieved by reacting an alcohol with a large excess of an ortho ester in the presence of MgCl 2 . 2 This method has also been applied to the synthesis of a mixed ortho ester of a homoallyl alcohol. Using the substrates in almost equimolar amounts leads, of course, to mixtures of products derived from mono-, bis-and tris-exchange.When the reaction of the homoallyl alcohol with the orthoformate is not performed with MgCl 2 , but in the presence of other Lewis acids like SnCl 4 , 3a,b SnBr 4 , 3a,b ZnBr 2 , 3a,b MgI 2 3b or Mg(CO 2 CF 3 ) 2 , 3b the stereoselective formation of tetrahydropyrans is observed. It can be assumed that the reaction sequence starts with the Lewis acid mediated transformation of the orthoformate A into the electrophilic dioxenium cation B, 4 which in turn is attacked by the allyl alcohol C as a nucleophile to yield the mixed ortho ester D. The latter is transformed into the dioxenium ion E -again in a Lewis acid mediated reaction. The sequence is completed by the intramolecular cationic olefin cyclization of E to give the tetrahydropyran F (Scheme 1). 3,5 Such intramolecular Prins reactions have been developed into an efficient method for the synthesis of tetrahydropyrans. 6 In particular, allylsilanes and related compounds have been employed as intramolecular traps for oxocarbenium ions which are generated in various ways. 7During the course of our studies towards the construction of pyrans and pyrones by means of cationic cyclizations 8 we focused on the development of a general method for the use of ortho esters as precursors for dioxenium ions in intramolecular olefin cyclizations. For this purpose, we chose the reactions between 1-arylbut-3-en-1-ols and orthoformates. To start with, 1-phenylbut-3-en-1-ol (1a) was prepared in 90% yield by reacting benzaldehyde with allylmagnesium bromide in Et 2 O. 9 Subsequently, one equivalent 1a was reacted with one equivalent trimethyl orthoformate (TMOF, 2) in the presence of one equivalent of InCl 3 at room temperature (Scheme 2). InCl 3 is a reagent that has proved to be an efficient Lewis acid in a number of Prins reactions. 10 The transformation proceeded cleanly and without any side reactions. Surprisingly, instead of the expected t...

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“…13,14 The difficulties associated with synthesising mixed ortho esters have recently been discussed by Beifuss et al 15 General access to mixed ortho esters is quite limited because the standard procedures involve the use of trimethyl orthoacetate with an acid catalyst, require long reaction times and further purification. 14,16,17 The last of these is problematic, owing to the instability of these compounds towards silica gel. 17 As part of our studies on the chemistry of cyanohydrins derived from enals 1 (Table 1), we required a method for the synthesis of mixed ortho ester derivatives of these compounds.…”

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confidence: 99%

“…As a consequence of the difficulties encountered with the established methods, 14,16,17 we investigated the simple addition of ketene dimethyl acetal 4 to 1, without solvent or acid catalyst (Equation 1). The addition reaction proceeded rapidly, with the evolution of heat, resulting in the formation of the mixed ortho ester 3 in high purity and in quantitative yield.…”

mentioning

confidence: 99%