Crotyl alcohol, oxidation

Scheme 11 Carbonyl tert-prenylation, crotylation, and allylation from the aldehyde or alcohol oxidation level under the conditions or iridium-catalyzed transfer hydrogenation...

More recently, using the cyclometallated iridium C,(7-benzoate derived from allyl acetate, 4-methoxy-3-nitrobenzoic acid and BIPHEP, catalytic carbonyl crotylation employing 1,3-butadiene from the aldehyde, or alcohol oxidation was achieved under transfer hydrogenation conditions [274]. Carbonyl addition occurs with roughly equal facility from the alcohol or aldehyde oxidation level. However, products are obtained as diastereomeric mixtures. Stereoselective variants of these processes are under development. It should be noted that under the conditions of ruthenium-catalyzed transfer hydrogenation, conjugated dienes, including butadiene, couple to alcohols or aldehydes to provide either products of carbonyl crotylation or p,y-enones (Scheme 16) [275, 276]. 

On the other hand, the regioselectivity is not seriously affected by the choice of reaction solvent. Even when THF is used in the reaction with crotyl alcohol, the 2-isoxazoline-5-methanol regioisomer is the only product produced (Scheme 11.31). The reaction rate is decreased in THF, but is still much faster than that in the absence of magnesium ions. Kanemasa et al. (130) concluded that the magnesium-mediated nitrile oxide cycloadditions to allylic alcohols compete with the thermal... 

Catalysis of the oxidation of allyl and crotyl alcohols with chloramine-T, 375 chloramine-B, bromamine-T, and bromamine-B Catalysis of the chloramine-T oxidation of glycolic and lactic acids 376... 

The oxidation of benzoin with cerium(IV) in perchloric acid solution is proposed to involve an interaction between Ce4+(aq.) ions and the keto alcohol, resulting in the formation of free radicals. The final product is benzoic acid.66 The rate of oxidation of crotyl alcohol with cerium(IV) is independent of the concentration of Ce(IV). The reaction induced polymerization of acrylonitrile indicating the formation of free radicals. The kinetics and activation parameters for the reaction have been determined.67 For the Ir(III)-catalysed oxidation of methyl ketones68 and cyclic ketones69 with Ce(IV) perchlorate, successive formation of complex between the reductant and Ce(IV) and then with the catalyst has been proposed. Results showed that in acidic solutions, iridium(III) is a more efficient catalyst than osmium and ruthenium compounds. 

Let us turn now to the other coupling partner, aldehyde 58 it was synthesised by the pathway shown in Scheme 17.18. The first step was a Sharpless catalytic asymmetric epoxidation on ( )-crotyl alcohol with the oxidant derived from (—)-diethyl tartrate. An in situ derivatisation with r-butyldiphenylsilylchloride was then performed. The desired epoxide 59 was readily isolated in 76% overall yield after chromatography. Treatment of 59 with 2-lithio-l,3-dithiane in THF and 1,3-dimethyl-3,4,5,6-tetrahydro-2(l/7)-pyrimidinone (DMPU also known as N,N-... 

An orf/io-directed lithiation allows the conversion of 25 to aryl iodide 40. Reductive ether formation of aldehyde 40 with crotyl alcohol yields compound 41. Intramolecular Heck reaction of 41 affords a mixture of the olefins 42 and 43. The undesired alkene 42 can be isomer-ized quantitatively to the desired enol ether 43 with Wilkinson s catalyst. Sharpless dihydroxylation ee 94 %) of the enol ether 43 provides lactol 44, which is oxidized directly to lactone 45. Finally, the pyridone-O-methyl ester is cleaved under acid conditions (45 — 7). 

Reaction of cis- and trans-crotyl alcohol in methanol solvent at 30 °C using hydrogen peroxide as oxidant. 

Figure 7. Oxidation of crotyl alcohol in water at 30 °C conversion oxirane selectivity triol selectivity.

Figure 9. Oxidation of crotyl alcohol in ethanol at 30 C conversion oxirane selectivity A ether diols triol selectivity.

Selective reduction of the carbonyl group of a,/S-unsaturated aldehydes and ketones has been achieved by a vapor-phase hydrogen transfer reaction using saturated primary and secondary alcohols as hydrogen donors. The preferred catalyst for the reaction, which is reversible, is magnesium oxide. Application to the reduction of acrolein to allyl alcohol, methacrolein to methallyl alcohol, crotonaldehyde to crotyl alcohol, and methyl isopropenyl ketone to 3-methyl-3-buten-2-ol is described. 

Figure 2A Proposed mechanism for the base-free, aqueous selective aerobic oxidation of crotyl alcohol to crotonaldehyde over PVP-stabilized Au core/Pd shell nanoparticles highlighting the importance of Pd + centers. (Reprinted with permission from Ref [78]. Copyright 2011, American Chemical Society.)...

Figure 2.7 Crotyl alcohol selox over Pd/AI Oj is a strong function of support morphology and Pd oxidation state, with atomically dispersed Pd + centers obtained over mesoporous alumina offering maximum crotonaldehyde production. (Adapted with permission from Ref [35]. Copyright Wiley-VCH Verlag GmbH. Co. KGaA.)...

Zbieg JR, Moran J, Krische MJ (2011) Diastereo- and enantioselective ruthenium-catalyzed hydrohydroxyalkylation of 2-Silyl-butadienes carbonyl ryn-crotylation from the alcohol oxidation level. J Am Chem Soc 133 10582-10586... 

Balcha T., J. R. Strobl, C. Fowler, P. Dash and R. W. J. Scott, Selective Aerobic Oxidation of Crotyl Alcohol Using AuPd Core-Shell Nanoparticles, ACS Catal, 1, 425-436... 

---