Butyldimethylsilyl-1,3-dithiane

Physical Data bp 115 °C70.03 mmHg, 124 °C/5 mm Hg, dl. 010. Solubility insoluble in H2O soluble in organic solvents. 

Form Supplied in commercially available as colorless liquid. Preparative Methods prepared by alkylation of 2-Uthio-l,3-di-thiane with i-butyldimethylsilyl chloride (eq 

Silylation of Alcohols. The silylphosphine serves as a silyl group source for the silylation of alcohols in the presence of DEAD and PPTS. Primary and secondary hydroxy groups are rapidly converted to the TBDMS ether under acidic conditions (eq 9). Other silyl groups could also be introduced by using silylphos-phines having the corresponding silyl group. 

Related Reagents. Trimethylsilyldiphenylphosphine tri-ethylsilyldiphenylphosphine triisopropyldiphenylphosphine (f-butyldimethylsilyl)phenylmethylphosphine bis(f-Butyl-dimethylsilyl)phenylphosphine tris(trimethylsilyl)phosphine trimethylsilyldiethylphosphine. 

Handling, Storage, and Precaution use in a fume hood unpleasant odor. 

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Intermediate 10 must now be molded into a form suitable for coupling with the anion derived from dithiane 9. To this end, a che-moselective reduction of the benzyl ester grouping in 10 with excess sodium borohydride in methanol takes place smoothly and provides primary alcohol 14. Treatment of 14 with methanesulfonyl chloride and triethylamine affords a primary mesylate which is subsequently converted into iodide 15 with sodium iodide in acetone. Exposure of 15 to tert-butyldimethylsilyl chloride and triethylamine accomplishes protection of the /Mactam nitrogen and leads to the formation of 8. Starting from L-aspartic acid (12), the overall yield of 8 is approximately 50%, and it is noteworthy that this reaction sequence can be performed on a molar scale. 

A 2-cyclopropyl-l,3-dithiane derivative reacted with butyllithium followed by fert-butyl-chlorodimethylsilane at low temperature to give the 2-rert-butyldimethylsilyl-2-cyclopropyl-l, 3-dithiane derivative in 36% yield. ... 

AllylsUanes are reactive towards 1,3-dithienium tetrafluoroborate. The intermediate -silyl carbocation typically suffers elimination of the silyl cation to furnish a 2-allyl-1,3-dithiane (eq 5). This protocol was employed to homologate allylsilane 3 to produce dithiane 4, an intermediate in the synthesis of epiantillatoxin (eq 6). A fert-butyldimethylsilyl ether used as a protecting group was cleaved from 3 during this reaction. 

Lithio-2-t-butyldimethylsilyl-l,3-dithiane (1). Reagent 1 is generated from 2-t-butyldimethylsilyl-l,3-dithiane by treatment with n-butyllithium, t-butyllithium, or lithium diisopro-pylamide (LDA) in THE at — 78°C followed by warming to approximately — 45°C (eq 2) although lithiation at higher temperatures is also reported (—30°C to 0°C). Hexamethylphosphoramide (HMPA) often is employed as a co-solvent. Diethyl ether (Et20) also can be used as the solvent of choice for lithiation. ... 

Alkylations. Treatment of 1 with various primary alkyl halides provides the corresponding substituted dithianes (eqs 3-5 ). Removal of the dithiane under the Lewis acid conditions, illustrated in eqs 3-5, unmasks the acyl silane for subsequent transformations such as photolysis, radical reactions, and heterocyclic synthesis. Other conditions for removing the dithiane moiety of 2-substituted-2-f-butyldimethylsilyl-l,3-dithianes include anodic oxidation, ceric ammonium nitrate (CAN)/NaHC03 in CH3CN/H2O, iodomethane/CaC03 in THF/H20, 8 and l2/CaC03 in THF/H2O. The formyl sUane of 2-t-butyl-dimethylsilyl-l,3-dithiane has also been reported." ... 

The three-component process with 2-t-butyldimethylsilyl-l,3-dithiane has been further optimized to incorporate two different epoxides, employing solvent as a means to control the 1,4-Brook rearrangement (eq 9). In this protocol, lithiation and alkylation of the first epoxide are conducted in Et20 rather than THF to prevent premature silyl migration. Introduction of HMPA (or DMPU) with the second epoxide in Et20 initiates the Brook process subsequently leading to the desired unsymmetrical, three-component adducts. 

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