A practical and efficient synthesis of .alpha.,.beta.-unsaturated acylsilanes

Danheiser, Rick; Fink, David M.; Okano, Kōji; Tsai, Yeun-Min; Szczepanski, Steven W.

doi:10.1021/jo00225a083

Cited by 72 publications

(24 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Oxidation of allylic carbinolsAn excellent synthesis of˛,ˇ-unsaturated acyl silanes from allyl silyl ethers is shown in Scheme 4020 . This simple two-step procedure hinges on the Wittig rearrangement127,128 , 24 PATAI's Chemistry of Functional Groups, Online © 2009 John Wiley & Sons, Ltd.…”

mentioning

confidence: 99%

Acyl Silanes

Page¹,

McKenzie²,

Klair³

et al. 2009

Patai's Chemistry of Functional Groups

View full text Add to dashboard Cite

show abstract

mentioning

confidence: 99%

Acyl Silanes

Page¹,

McKenzie²,

Klair³

et al. 2009

Patai's Chemistry of Functional Groups

View full text Add to dashboard Cite

show abstract

“…On the other hand, the synthesis of the E-isomer E-1a was started with ␣-keto-silane E-8 (a mixture of E-and Zisomers, E/Z = 10:1), prepared from E-crotyl TBDMS ether (E/Z = 10:1) via reverse Brook rearrangement, 7 while numerous attempts to prepare E-1a from the alkyne 3 were not satisfactory. For example, reduction of 3 using LiAlH 4 or Na/NH 3 gave an unidentifiable mixture of products.…”

Section: Resultsmentioning

confidence: 99%

Chirality transferring [3,3] sigmatropic rearrangement of (1‐acyloxy‐2‐alkenyl)trialkylsilane synthesis of optically active vinylsilane‐containing α‐amino acid

2001

View full text Add to dashboard Cite

A vinylsilane-containing alpha-amino acid and alpha,alpha-disubstituted alpha-amino acid 2 having two contiguous asymmetric carbon centers at their alpha and beta positions were synthesized in an optically active form by ester-enolate Claisen rearrangement of the alpha-acyloxysilane 1 as the key step, where the chirality of an alpha-acyloxy-TBDMS group was completely transferred to the rearranged product.

show abstract

“…However, instead of the expected C ‐trimethylsilylated product 6 a , the C ‐triethylsilylated product 7 a was obtained as a major product in a stereochemically pure form (Table 1, entry 1). This result was particularly surprising, considering that the relative ease of migration of silyl groups has been reported as [1,2]≫[1,4],5a, 6c, 9 and that α‐silyloxyalkylstannane derivatives undergo rapid retro‐[1,2]‐Brook rearrangement (<15 min) under the same conditions 3e. Silyl groups of various size migrate in high yields and the predominance of [1,4] migration over [1,2] migration is general (Table 1).…”

Section: Methodsmentioning

confidence: 99%

Regioselective Aliphatic Retro‐[1,4]‐Brook Rearrangements

2008

View full text Add to dashboard Cite

The migration of silicon is a ubiquitous process in reactions, and the Brook rearrangement is an intramolecular migration of a silicon atom from a carbon to an oxygen atom.[1] The reverse process-migration of a silicon atom from an oxygen to a carbon atom-is referred to as the retro-or reverseBrook rearrangement and is a common occurrence.[2] Studies on retro-[1,2]-Brook rearrangements have revealed that the rearrangement is highly stereospecific with regard to the configuration at the carbon atom and proceeds with retention of configuration in the a-silyloxy carbanions generated from aliphatic substrates, whereas inversion is observed for benzylic and allylic carbanions.[3] As the retro-Brook rearrangement requires excess base, the driving force for the reaction may be the formation of a lithium alkoxide that is more stable than the starting organolithium compound. Higher-order retro-[1,3]-, -[1,4]-, -[1,5]-, and -[1,6]-Brook rearrangements have also been the subject of numerous investigations, and have been utilized for the preparation of functionalized organosilane derivatives. [4][5][6][7][8] The general trend of the ease of silyl migration has been reported to be] based on the logic that the shorter transfer distance is more favored, [9] and this order of migration has long been accepted without question.[5a, 6c] It has recently been reported that the regioselectivity of the retro-[1,2]-and [1,4]-Brook rearrangements in an allyllithium system depends upon the reaction conditions, and that the addition of hexamethylphosphoramide (HMPA) as a cosolvent improves the [1,4] selectivity.[5l] However, there has been no study of competitive silyl migration occurring in aliphatic retro-Brook rearrangements. We decided to investigate the relative ease of otherwise comparable [1,2] and [1,4] migrations. We report here the first documented example of the preference of retro-[1,4]-migration over retro-[1,2] migration in an a,g-disilyloxy organolithium system.To evaluate the regioselectivity of the retro-Brook rearrangement, we examined 1,3-disilyloxy-1-tributylstannylbutane derivatives 1, which can form [1,2] and [1,4] products 2 and 3, respectively, after transmetalation and rearrangement (Scheme 1). The optically active stannanes 4 and 5 were synthesized in a pure form by the reaction of tributylstannyllithium [10] and an aldehyde prepared from methyl (R)-3-hydroxybutylate (98 % ee) followed by silylation and separation by flash chromatography (Scheme 2). The configurations of 4 and 5 were determined to be syn and anti, respectively, by formation of the acetonide [11] and by 13 C NMR analysis using the Rychnovsky method.

show abstract

A practical and efficient synthesis of .alpha.,.beta.-unsaturated acylsilanes

Cited by 72 publications

References 1 publication

Acyl Silanes

Acyl Silanes

Chirality transferring [3,3] sigmatropic rearrangement of (1‐acyloxy‐2‐alkenyl)trialkylsilane synthesis of optically active vinylsilane‐containing α‐amino acid

Regioselective Aliphatic Retro‐[1,4]‐Brook Rearrangements

Contact Info

Product

Resources

About