N-Isocyanates, N-Isothiocyanates and Their Masked/Blocked Derivatives: Synthesis and Reactivity
Bibliographic record
Abstract
In contrast to C -substituted isocyanates which are frequently used reagents in synthesis, nitrogen-substituted isocyanates ( N -isocyanates) remained a scientific curiosity in the literature for over a century. The amphoteric character of these reactive intermediates, which results in their propensity to dimerize, prevented the development of their full synthetic potential. In this review, the pioneering work that led to the development of reliable methods for their synthesis, established the existence of such species by spectroscopy, and allowed a delineation of their basic reactivity is presented. The high reactivity of these intermediates has been controlled through the use of masked precursors to regulate their concentration via a reversible equilibrium, a strategy which is also used in industrial processes utilizing C -isocyanates. This control led to the development of more complex reactions, including reaction cascades that allow the rapid synthesis of heterocycles possessing the N–N–C=O motif, which is widely present in agrochemicals and pharmaceuticals. This review covers the literature of N -isocyanates and their sulfur analogues, N -isothiocyanates, until April 2016. 1 Introduction 2 Formation of N -Isocyanates 2.1 Rearrangement of Carbamoyl Azides 2.2 Ring Opening of Heterocycles 2.3 Thermolysis of Hydrazine Derivatives 3 Formation of N -Isothiocyanates 4 Isolation and Observation 4.1 Isolation and Observation of N -Isothiocyanates 4.2 Isolation and Observation of N -Isocyanates 5 Reactivity 5.1 Reactivity of N -Isothiocyanates 5.2 Reactivity of N -Isocyanates 6 Conclusion
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".