Double deprotonation

Deprotonation of H2O2 yields OOH , and hydroperoxides of the alkali metals are known in solution. Liquid ammonia can also effect deprotonation and NH4OOH is a white solid, mp 25° infrared spectroscopy shows the presence of NH4+ and OOH ions in the solid phase but the melt appears to contain only the H-bonded species NH3 and H202. " Double deprotonation yields the peroxide ion 02 , and this is a standard route to transition metal peroxides. 

Next, examine the dianion resulting from double deprotonation of ethyl acetoacetate. Draw all the resonance contributors needed to describe this ion. Next, examine the geometry, atomic charges and electrostatic potential map for dianion. Are you able to decide which resonance contributors are important and which are not ... 

The reaedvity of carbon is much enhanced by the double deprotonated intermediates of nitro compounds. Except for nitromuhane, other nitroalkanes are alkylated to give the C-alkylated products in 50-60% yield by this procedure fsee Eq. 5.4. ... 

A suspension of 3.324 g (lO.Ommol) of (/ )-2-hydroxy-1,2,2-triphenylelhyl acetate in 40 mL of THF is stirred under nitrogen at — 78°C in a 250-mL. two-necked flask equipped with a three-way stopcock connected to a vacuum pump and a nitrogen line, septum, and magnetic stirring bar. After dropwise addition of the LDA solution, the mixture is stirred in an ice bath for 1 h to complete the double deprotonation. 

The spirolactone is obtained in a diastereomeric ratio of 95 5 when the following dilithium reagent, available by double deprotonation of the acid, reacts with 2,2-dimcthylpropanal (pi-... 

A similar case of enolatc-controlled stereochemistry is found in aldol additions of the chiral acetate 2-hydroxy-2.2-triphenylethyl acetate (HYTRA) when both enantiomers of double deprotonated (R)- and (S)-HYTRA are combined with an enantiomerically pure aldehyde, e.g., (7 )-3-benzyloxybutanal. As in the case of achiral aldehydes, the deprotonated (tf)-HYTRA also attacks (independent of the chirality of the substrate) mainly from the /te-side to give predominantly the t/nii-carboxylic acid after hydrolysis. On the other hand, the (S)-reagcnt attacks the (/ )-aldebyde preferably from the. S7-side to give. s wz-carboxylic acids with comparable selectivity 6... 

Double deprotonation of tetrahydro-2-(2-nilroethoxy)-2//-pyran (8) and reaction with electrophiles provides a variety of substituted and functionalized nitroaldols1 Reaction with aldehydes affords 2-nitro-l,3-alkanediols 9 in 44 90% yield and high diastereoselectivities. From analogy of their II-NMR spectra and comparison with known compounds, the (R, R ) relative configuration is likely15. 

In a similar approach, double deprotonation of r 6-coordinated ortho- and para-cresols, 30 and 31, with t-BuOK led to formation of stable r 4-coordinated p- and o-quinone methide complexes of manganese, 32 and 33 (Scheme 3.19).37... 

Another method for improving the reactivity of nitro compounds is provided by the double deprotonation of nitroalkanes. In this case, the reaction with ketones affords P-nitro alcohols in 40-60% yield (Eq. 3.19).30... 

Diboratacarbazole heterocycles 137 are obtained in 60% isolated yield by heating the phosphine-stabilized 2,2 -diborabiphenyl derivative 138 with primary amines in toluene for 20h (Scheme 55). Further double deprotonation of the heterocycle 137 (Ar = Ph) with a lithium amide leads to the dianionic 9,11-diboratacarbazole derivative 139 (98%, S nB 31.71 ppm). Structures 137 (Ar = Ph) and 139 were characterized by X-ray crystallography <20040M3085>. 

In general, nitronates undergo O-alkylation. However, some procedures have been developed that overcome the preference for O-alkylation in favour of C-alkylation. For example, the double deprotonated nitronates introduced by Seebach74 can be C-alkylated and this strategy was used for the synthesis of nitro furanosyl and pyranosyl compounds.75... 

A special case are the reactions in which a double deprotonation of a nitrocompound is involved [20], because then the "Lapworth model" does not apply anymore and the rule of alternating polarities is clearly violated (reaction 3, Scheme 2.3 see also Heading 5.5.5) ... 

The synthetic implications [21] of either a conjugated double bond or the double deprotonation in derivatives of nitroethane are summarised below (Scheme 2.4) ... 

Therefore, the N(9) radical should be more stable than the N(6) one. That is why both radicals coexist in the system and both N(9) and N(6) deprotonations take place. In the case of the guanine cation-radical, the presence of the carbonyl group in the pyridazine ring brings about two additional effects Deprotonation infringes on this ring exclusively, and double deprotonation leads to the formation of a distonic anion-radical. Scheme 1.25 depicts the differences mentioned. Adhikary et al. (2006) substantiated it experimentally (ESR and UV) and theoretically (B3LYP). 

The stereoselective introduction of both benzyl groups simultaneously in one step seemed to be particularly attractive for a short synthesis of a- hy-droxylated lactone lignans from malic acid (99). Such a simultaneous double alkylation requires the formation of a chiral l,3-diene-l,4-diolate, which was not known. On the other hand, achiral 1,3-diene-1,4-diolates (di-enolates) have been previously prepared by Garrett et al. [58] and subsequently employed for the synthesis of racemic lignans by Snieckus [59] and Pohmakotr [60]. With knowledge of the synthesis and reactivity of di-enolates, we planned to prepare chiral di-enolates from dioxolanones and to alkylate these di-enolates in a stereocontrolled manner (Scheme 22). For the development of the described double deprotonation/alkylation strategy, tert-hutyl... 

Table 1 Conditions for the attempted double deprotonation of dioxolanones 100 and 101...

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