Catalytic reduction of benzoate esters and lactones in the presence of PhMeSiH<sub>2</sub> and a titanocene-based catalyst
Bibliographic record
Abstract
PhMeSiH2 reduces ethyl benzoate in the presence of a Cp2TiMe2 (Cp = η5-cyclopentadienyl) catalyst to give PhMeSi(OEt)(OCH2Ph) (1). Small to moderate amounts of toluene are also produced, depending on the reaction conditions. Under 40 psi of H2 the same reaction gives quantitative reduction of the ester to toluene. PhCHO is reduced, under the same conditions as the ester, to a mixture of PhMeSi(OCH2Ph)2 and toluene in proportions similar to that observed with the ester. A stoichiometric reaction of PhMeSiH2, PhCOOEt, and Cp2TiMe2 resulted in the formation of known [Cp2Ti(OEt)]2 (2) in 75% isolated yield. A mechanism is proposed in which the C=O of the ester inserts into a TiH bond. A Ti-mediated transfer of the ethoxy group from the resulting (α-ethoxy)benzyloxytitanium intermediate to silicon produces PhMeSi(OEt)H and PhCHO. 1 is generated via hydrosilation of PhCHO by PhMeSi(OEt)H. Both β- and γ-butyrolactones react with PhMeSiH2 in the presence of a catalytic amount of Cp2TiMe2 to produce copolymers -[O-PhMeSi-O(CH2)3CHR]n- (R = H, 3; R = Me, 4) (Mw [Formula: see text] 1 × 103; Mw/Mn [Formula: see text] 1.3). A mechanism analogous to that proposed for the ethyl benzoate reduction is proposed. A reaction of PhMeSiH2 and γ-butyrolactone with a stoichiometric amount of Cp2TiMe2 in the presence of tetrahydofuran (THF) produces Cp2Ti(µ-H)(µ-η1,η5-C5H4)Ti(OC4H8)Cp(5) (65% isolated yield) whose structure is determined by X-ray crystallography.Key words: hydrosilation, esters, lactones, titanocene, catalysis.
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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) | 0.002 | 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".