Heterocage compounds. IV. Through-sigma-bond interaction of .beta.-amino Ketone moiety in 1,3-diazaadamantan-6-one and 3,6-diazahomoadamantan-9-one systems. Structure and reactivity

Abstract

Some characteristic structural features of 5,7-diphenyl-(la) and 5,7-dicarbomethoxy-l,3-diazaadamantan-6one (lb) and 1,8-diphenyl-(2a) and l,8-dicarbomethoxy-3,6-diazahomoadamantan-9-one (2b) are discussed in terms of uv, nmr, and ir spectral data, and pKJ values. The /3-amino ketone moiety in these compounds was shown to behave as an amide analog because of the through-c-bond interaction of the lone electron pair on the nitrogen atom with the carbonyl r orbitals. Reaction of la with tosylhydrazide afforded no trace of the corresponding hydrazone but only 6-alcohol 8. Reaction of la with excess hydrazine hydrate in refluxing diethylene glycol gave hydrazone 7, which, on treatment with potassium ieri-butoxide in dimethyl sulfoxide, gave also 8.

Assessable Consequences of Through‐Bond Donor–Acceptor Interactions in β‐Aminoketones

“…The λ max values do not deviate significantly between the di‐ and triketones in this work, although a survey of the literature shows that simple (even rigid) β‐aminoketones offer values ≈235–245 nm; this increases for the diaza‐adamantanones 4a. 5d Interestingly, the σ‐coupled transition can be reversibly abolished4a upon protonation by trifluoroacetic acid in acetonitrile (Figure 8; see the http://www.wiley-vch.de/contents/jc_2111/2008/f701220_s.pdf for additional details)…”

“…Even so, it seems unnecessary, and likely inappropriate,31f to equate the magnitude of the bond length changes to the “strength” of the through‐bond interactions in the molecules; suffice it to say, the consequences of donor–acceptor interactions in these aza‐adamantanones are detectable. That pathway a ‐ b ‐ c ‐ d emerges as unique (one donor nitrogen communicating with two acceptor carbonyls) is analogous to the “enhanced” through‐bond effects noted for the diaza‐adamantanones like 3 b (that feature two donor nitrogens communicating with one acceptor carbonyl) 5d…”

“…Notwithstanding the obvious complications of solvation (and experimental conditions in general), differences identified from single‐point comparisons (e.g. 1 versus 3 )5d are difficult to attribute to any one particular phenomenon, although this is often done. Additional complication enters when considering IR data for the aza‐ and deaza‐adamantanones bearing two or more ketones in a 1,3‐relationship that display Fermi‐type coupling;38 we have used the average carbonyl stretch for making a quick comparison (the complete comparative data, including the data for 6 – 9 , is provided in the http://www.wiley-vch.de/contents/jc_2111/2008/f701220_s.pdf).…”

Copper–Bispidine Complexes: Synthesis and Complex Stability Study

“…Ligand 1b , with a carbonyl group at C9, demonstrates the lowest value for the first step of protonation. Such an influence of keto groups is traditionally associated with interaction of nitrogen’s lone pairs of aminogroups and a carbonyl group, similarly to amides, 63 due to through bond interaction between CO and N’s. 64−68 This leads to a decrease in the K a of bispidinones compared to that of bispidines by 4 orders of magnitude.…”

“…The second proton addition, with log K 1H – log K 2H = 4 for all considered ligands, also correlates with the second protonation step of pyridyl-containing bispidines, log K 1H – log K 2H = 4.5–6. 61,63 Protonation of the carboxylic groups in bispidines is expected to occur at an acidic pH, similar to that of glycine in 2 and α-alanine in 3 . However, it becomes possible to determine the third step of protonation related to the carboxylic group only for 3 , log K 3H – log K 2H = 2.5–2.6.…”