Isolation and characterization of an unusually stable formamidinium-containing macrotricyclic complex of lithium ion formed during the synthesis of 14-thia-1,4,8,11-tetraaza-bicyclo[9,5,3]nonadecane
Bibliographic record
Abstract
Using 1,3-bis(chloroacetamido)propane (5) as the common intermediate, an efficient route is described to the stepwise syntheses of 1-thia-4,8-diazacyclodecane, [10]aneN2S (8), and the pentadentate macrobicycle 17-thia-1,4,8,11-tetraazabicyclo[9,5,3]-nonadecane (11). During the investigation of the condensation of (5) with (8), with Li2CO3 used as a base the Li+ cation is carried over as the complex of the dioxo intermediate (10) and survives further reduction. Prolonged contact of these complexes with CHCl3 during cyclisation and extraction (in the presence of Li2CO3 and NaOH, respectively), leads to the formation of the complex cation [Li(4)]2+ as a byproduct in which the cationic macrocycle (4), containing a formamidinium ring, is formed through bridging of the 1,11-nitrogens in the macrobicycle (11) by a -CH= group that is derived from CHCl3. This renders the cavity in (4) too small for the inclusion of transition metal ions. Reaction of the lithium cation [Li(4)]2+ with PdCl2 yielded the trimetallic salt [(Li(4)]-PdCl2-[(Li(4)])](ClO4)4 in which two [Li(4)]2+ ions are bridged by a PdCl2 unit through coordination of the pendant thioether donors. A crystal structure of this trimetallic salt confirms the formation of [Li(4)]2+. In contrast, if triethylamine is used as a base during the cyclisation reaction leading to the formation of (11) and contact with aqueous NaOH and CHCl3 during its isolation is minimized, the formation of (4) is prevented and the yield of (11) improved.Key words: macrobicycle synthesis, lithium, formamidinium, paaladium, complex.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".