Manganese enolates

Regioselective monoalkylation of 2-methylcyclohexanone (3.4) with PhCH2Br via its manganese enolate 3.7 gives 2-benzyl-6-methylcyclohexanone (3.8). ... 

REGIOSELECTIVE MONOALKYLATION OF KETONES VIA THEIR MANGANESE ENOLATES 2-BENZYL-6-METHYLCYCLOHEXANONE... 

To this solution of the manganese enolate are added successively (each over 5 min) 80 mL of 1-methyl-2-pyrrolidinone (NMP) (Note 7) and 12.2 g (71.3 mmol) of benzyl bromide (Note 8). The resulting mixture is stirred for 2 hr and hydrolyzed by the dropwise addition of 100 mL of a 1 M aqueous hydrochloric acid solution (HCI) over 15 min. Petroleum ether (35-60°C, 100 mL) is added, and the aqueous layer is separated and extracted three times with 50-mL portions of diethyl ether. The combined organic layers are washed with 100 mL of an aqueous saturated sodium carbonate solution, dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure with a rotary evaporator to afford 13.7-22.3 g of a brown oil (Note 9). Short path distillation under reduced pressure affords 8.8-8.9 g (87-88%) of 2-benzyl-6-methylcyclohexanone as a pale yellow oil, bp 95-100°C (0.3 mm) (Note 10). 

REGIOSELECTIVE MONOALKYLATION OF KETONES VIA THEIR MANGANESE ENOLATES 2-BENZYL-6 METHYLCYCLOHEXANONE FROM 2-METHYLCYCLOHEXANONE (Cyclohexanone, 2-methyl-6-(phenylmethyl)-)... 

MONOALKYLATION. REGIOSEL CTIVE, OF KETONES, VIA MANGANESE ENOLATES, 76. 239... 

Construction of furan ring of 131 by acid-catalyzed cyclization of 134 cannot be achieved due to low reactivity of the a,a-difluorinated double bond toward protonation. Therefore, the following sequence was employed for the total synthesis of 131 (Scheme 12.20) fluorination of lactone 133, introduction of a double bond to 136 by Wittig olefination, and modification of R part of O ." " The use of manganese enolate of lactone 133 is useful for one-pot difluorination. The reaction of the lithium enolate of 133 with the conventional electrophilic fluorinating reagent such as N-fluorobenzenesulfonimide provides only monofluoride 135. 

Using the manganese enolates, the chiraUty is transfered from the chiral ester moiety towards the peptide backbone, but not inside the peptide backbone. Therefore, the influence of the chelating metal salt in the rearrangement of several dipeptide crotyl esters was investigated. 

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