Magnesium ferf-butyl- chloride

Neopentyl alcohol has been made by lithium aluminum hydride reduction of trimethylacetic acid and by treating ferf-butyl-magnesium chloride with methyl formate. ... 

B. 2-Chloro-3,6-di-tert-butyl-l,4-benzoquirwne. A 2-1. Erlenmeyer flask is charged with a solution of 112 g. (0.385 mole) of 2,3-dichloro-2,5-di-fer<-butylcyclohex-5-ene-l,4-dione in 800 ml. of ether. A solution of 28.4 g. (0.383 mole) of diethylamine (N-ethylethanamine) in 50 ml. of ether is added in one portion to the vigorously swirled flask (Note 5). The reaction is instantaneous, resulting in a voluminous precipitate. The mixture is washed with two 1-1. portions of water and then with 500 ml. of aqueous saturated sodium chloride. The yellow ether solution is dried over anhydrous magnesium sulfate, the drying agent removed by filtration, and the solvent removed on a rotary evaporator to yield 96-97 g. (98-99%) of 2-chloro-3,6-di-ferf-butyl-l,4-benzo-quinone as a yellow oil which is used without further purification (Note 6). 

To prove this hypothesis a suitable substrate, l-diazo-3-methyl-3-[(E)-phenyldiazenyl]butan-2-one (42) was used. Methyl 2-(2-arylhydrazino)-2-methylpropanoate (39) reacting with a bulky Grignard reagent like isopropyl magnesium bromide gives 4,4-dimethyl-2-phenyl-l,2-diazeti-din-3-one 40 (87TL6577). Oxidation with ferf-butyl hypochlorite converts diazetidinone 40 into 2-methyl-2-(phenyldiazenyl)propanoyl chloride 41, which upon treatment with diazomethane affords the desired diazo ketone 42 (Scheme 8) (98ACE2229). 

The deprotection of f-Boc proline ester 2a is representative of the general procedure employed. ferf-Butyl carbamate (0.217 g, 1.0 mmol) and aluminium chloride (0.134 g, 1.0 mmol) doped on a neutral alumina (1.0 g) were mixed thoroughly on a vortex mixer. The reaction mixture was placed in an alumina bath inside an unmodified household microwave oven (operating at frequency 2450 MHz) and irradiated for a period of 1 min. After completion of the reaction (monitored by TLC, EtOAc-hexane, 9 1 v/v), it was neutralized with aqueous sodium bicarbonate solution and the product was extracted into ethyl acetate (2x15 mL). The ethyl acetate layer was separated, dried over magnesium sulfate, fdtered, and the crude product thus obtained was purified by column chromatography to afford pure methyl ester 2b in 88% yield. 

The synthesis of enantioenriched acyl chloride 54 was originally conducted using a modification of procedures described by Villieras and coworkers for the preparation of racemic alcohol 55 (Scheme 12). Thus, the synthesis commenced with the preparation of racemic allylic alcohol 55 from 2,5-dimethoxytetrahydrofuran. The alcohol was resolved enzymatically, following procedures reported by Ogasawara, to provide enantioenriched alcohol (S)-55 in 50% yield and 99% ee. Protection of the alcohol with the sterically encumbered ferf-butyl dimethylsilyl group allowed a diastereoselective copper(I)-mediated conjugate addition of methyl magnesium bromide to... 

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