Reduction Wagner-Meerwein rearrangement

Selective reduction of t-alkyl halides. The ate complex of B-butyl-9-BBN with n-BuLi selectively reduces tertiary alkyl halides to hydrocarbons in high yield without effect on primary or secondary halides. It does not reduce aryl or vinyl halfdes, but does reduce benzyl and allyl halides. The reduction involves a carbonium ion, and thus can proceed with Wagner-Meerwein rearrangements in certain systems. 

An interesting double ring expansion sequence developed by Vogel involves the initial pinacol coupling of cyclobutanone, isomerization to ketone 79 in acid, followed by reduction and Lewis acid-promoted Wagner-Meerwein rearrangement with dehydration (Scheme 19).129) For preparative purposes, 80 can be more... 

The selectivity was useful in a synthesis of nojigku alcohol (8) from (—)-isobornyl acetate (4). Oxidation of 4 with CrOj gave a mixture of 5 and 6, which was converted into 7 in high yield by Riley oxidation and reduction. The conversion of 7 into 8 involves elimination of the 5-keto group and Wagner-Meerwein rearrangement. ... 

Taskesenligil, Y., Bald, M. An unusual zinc-promoted reductive retro-Wagner-Meerwein rearrangement. Turk. J. Chem. 1996, 20, 335-340. 

Wadsworth-Emmons reaction, 151 Wagner-Meerwein rearrangement, 91, 509 Wichterle reaction, 472 Willgerodt-Kindler reaction, 496 Williamson synthesis, 520 Wittig reactions, 83, 333, 573 Wittig reagents, 83, 549, 573 Wolff-Kishner reduction, 378,414 Wolff rearrangement, 544... 

C2 symmetry), a high-symmetry chiral cage-shaped tricyclic hydrocarbon closely related to D2 twistane. Wagner-Meerwein rearrangement (144) of the unsaturated carboxylic acid (-)-151 provided the lactone (-)-168, which in turn was converted into the ketone (+)-170 via a series of intermediates, including the mesylate 169 whose intramolecular alkylation was a crucial step in this approach. Removal of the carbonyl group by Wolff-Kishner reduction completed the synthesis of (+)-brexane (171) (145). 

As demonstrated below, the general procedure begins by treatment of camphor with triflic anhydride and a non-nucleophilc base to give allyl triflate 107 via Wagner-Meerwein rearrangement of 105 followed by elimination. Reduction of 107 with LiAULj then results in allylic alcohol... 

A BASF group showed that rhodium-catalyzed reaction of a-(-)-pinene gives (-l-)-3-formylpinane (Scheme 4.53) [11]. In contrast, the use of Co2(CO)g led to the formation of (-)-2-formylbornane. The Wagner-Meerwein rearrangement is mediated by the intermediarily formed HCo(CO)4 with acidic properties. Prior isomerization of a- to P-pinene can be avoided by applying a high CO partial pressure and low temperatures. Based on this protocol and a subsequent reductive amination, chiral aminomethyl-plnane was prepared in the 100 g scale. 

The Leuckart reaction (reductive amination of carbonyl compounds with formamide and formic acid) of 2-norbornanone and (lR)-(V-(3,3-dimethyl-2-oxo-l-norbornyl) acetamide furnishes the expected A-(2-norbornyl)formamides. (l/()-AI-(7,7-Dimethyl-2-0X0-l-norbornyl)acetamide, on the other hand, gives a product resulting from a Wagner-Meerwein rearrangement of the usual cationic intermediate followed by an unprecedented transamination, which affords an A,A-diacylammonium ion. Hydrolysis gives (15 )-A-(3,3-dimethyl-2-oxo-l-norbornyl)acetamide, which then undergoes the normal Leuckart reaction. 

Oxidation and Reduction.—Oxidative rearrangement of olefins with thallium(m) nitrate in methanol provides a simple synthesis of aldehydes and ketones in high yields. Cleavage of the intermediate thallium compound proceeds via a transition state with high carbonium ion character, which leads either to carbonyl compounds (354) by Wagner-Meerwein rearrangement or to glycol methyl ethers (355). ... 

Paquette et al. prepared the dihomotropone 58 and concluded from its IR, UV, and NMR spectra that there was no evidence for the homoaromatic charge-separated species 59. Again, upon protonation, the dihomotropylium cation 60 was not detected. Acid treatment of the alcohol 61 from reduction of 58 gave facile Wagner—Meerwein rearrangement and no indication of the desired dihomotropylium cation 62. 

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