Aldehyde From allylic alcohol

ALDEHYDES FROM ALLYLIC ALCOHOLS AND PHENYLPALLADIUM ACETATE 2-METHYL- 3-PHENYLPROPIONAL-DEHYDE, 51, 17 ALDEHYDES FROM AROMATIC NITRILES p-FORMYLBENZENE-SULFONAMIDE, 51, 20 ALDEHYDES FROM 2-BENZYL-4,4,6-TRIMETHYL—5,6-DIHYDRO-l, 3-(4H)-OXAZINE 1-PHENYLCYCLO-PENTANECARBOXYALDEHYDE, 51,... 

ALDEHYDES FROM ALLYLIC ALCOHOLS AND PHENYLPALLADIUM ACETATE 2-METHYL-3-PHENYLPROPIONALDEHYDE... 

ALDEHYDES FROM ALLYLIC ALCOHOLS AND PHENYLPAL-LADIUM ACETATE 2-METHYL-... 

Under the proper conditions, the Jones reagent can give good yields (76-87%) of aldehydes from allylic alcohol s. 

A salient structural feature of intermediate 18 (Scheme 2b), the retrosynthetic precursor of aldehyde 13, is its y,r5-unsaturated ester moiety. As it turns out, the Johnson ortho ester variant of the Clai-sen rearrangement is an excellent method for the synthesis of y,<5-unsaturated esters.11 In fact, the Claisen rearrangement, its many variants included, is particularly valuable in organic synthesis as a method for the stereocontrolled construction of trans di- and tri-substituted carbon-carbon double bonds.12,13 Thus, it is conceivable that intermediate 18 could be fashioned in one step from allylic alcohol 20 through a Johnson ortho ester Claisen rearrangement. In... 

Previous syntheses of terminal alkynes from aldehydes employed Wittig methodology with phosphonium ylides and phosphonates. 6 7 The DuPont procedure circumvents the use of phosphorus compounds by using lithiated dichloromethane as the source of the terminal carbon. The intermediate lithioalkyne 4 can be quenched with water to provide the terminal alkyne or with various electrophiles, as in the present case, to yield propargylic alcohols, alkynylsilanes, or internal alkynes. Enantioenriched terminal alkynylcarbinols can also be prepared from allylic alcohols by Sharpless epoxidation and subsequent basic elimination of the derived chloro- or bromomethyl epoxide (eq 5). A related method entails Sharpless asymmetric dihydroxylation of an allylic chloride and base treatment of the acetonide derivative.8 In these approaches the product and starting material contain the same number of carbons. 

The high selectivity of the catalyst in forming ( )-alkenes can be used in interesting ways (eq. 1). For example, in acetone-iie solution, within 15 min at room temperature allyl alcohol is converted to nearly pure enol (E)-26. Under these mild conditions, the product slowly isomerizes to the more stable aldehyde tautomer. We know of one other report of rapid enol formation from allyl alcohol, using a Rh... 

Although the asymmetric isomerization of allylamines has been successfully accomplished by the use of a cationic rhodium(l)/BINAP complex, the corresponding reaction starting from allylic alcohols has had a limited success. In principle, the enantioselective isomerization of allylic alcohols to optically active aldehydes is more advantageous because of its high atom economy, which can eliminate the hydrolysis step of the corresponding enamines obtained by the isomerization of allylamines (Scheme 26). 

In Chapter 24 we mentioned the Swern oxidation briefly as an excellent method of converting alcohols to aldehydes. We said there that we would discuss this interesting reaction later and now is the time. The mechanism is related to the reactions that we have been discussing and it is relevant that the Swern oxidation is particularly effective at forming enals from allylic alcohols, the Swern oxidation... 

The chiral acetals of a,p-enals derived from (H,R)-( -I-)-N,N,N, N -tetramethyltartaric acid diamide (9, 47-48) undergo either 1,4- or I. . .-addition of R,AI with high asymmetric induction. The course of reaction can be controlled by the choice of solvent. 1,4-Addition is favored in 1,2-dichloroethane (or toluene) 1,2 addition is the main or only reaction in chloroform. The adducts can be converted into optically active p-alkyl aldehydes or allylic alcohols (Chart I). ... 

Compared with well-established electrophilic it-allylpalladium chemisty, the catalytic asymmetric reaction via umpolung of jt-allylpalladium has received very limited exploration [93]. Zhou and co-workers investigated the Pd-catalyzed asymmetric umpolung allylation reactions of aldehydes [22a, 94], activated ketones [95], and imines [96] by using chiral spiro ligands (5)-18e, (S)-17c, and (5)-17a, respectively. One representative example is that of the Pd/(5)-18e-catalyzed umpolung allylation of aldehydes with allylic alcohols and their derivatives, which provided synthetically useful homoallylic alcohols from readily available allylic alcohols, with high yields and excellent enantioselectivities (Scheme 33). 

Deprotonation of allyl tetramethylphosphorodiamidate, readily prepared from allyl alcohol, induces the migration of phosphorus from oxygen to carbon. A second deprotonation then occurs to give the dianion (33 Scheme 16). Alkylation with 1-iodopropane takes place at the 7-position to give hexanoic acid after hydrolysis. Reaction of (33) with aldehydes and ketones followed by hydrolysis gives 7-lac-tones, and a similar sequence with epoxides produces 6-lactones. 

Titanabicycloalkene intermediates derived from diynes or enynes in which the terminal sp-carbon bears a silyl group are alkylating agents. Thus, a subsequent reaction with aldehydes generates allylic alcohols. ... 

In contrast to the reaction with diisobutylaluminium hydride, hydroalumination of disubstituted alkynes with lithium hydridodiisobutylmethylaluminate, obtained from diisobutylaluminium hydride and methyllithium, results in anti addition across the triple bond. Subsequent reaction with aldehydes gives allylic alcohols, with CO2 gives a,p-unsaturated acids and with iodine gives alkenyl iodides, isomeric with the products obtained in the reaction sequences using diisobutylalvmiinium hydride. ... 

Masuyama and co-workers have shown that nucleophilic allyltrichlorostaimanes 329 are generated by the reaction of allyl carbonates with SnCl2 and react with aldehydes to give the homoallyl alcohols 330. DMI is a good solvent [121]. Also allyl alcohols can be used for the allylation. Formation of the allyltrichlorostannane 329 from allyl alcohol and SnCl2 was confirmed by NMR studies [122]. a-Methylenelactone 332 was obtained by the reaction of ethyl (a-hydroxyethyl)acrylate 331 with pentanal [123]. 

A new simple synthetic route to 2,5-dihydrooxazoles 71 by cycloaddition of allyl azido ethers 70 via triazoUnes was shown by Hassner et al. [37]. Earlier, they demonstrated that cr-azido ethers can be easily prepared from aldehydes using an alcohol, hydrazoic acid and titanium tetracliloride as well as the fact that thermolysis of azido ethers in the absence of a double bond forms imi-dates [35,36]. Using the above mentioned facts, the allyl azido ethers 70 were synthesized in good yields employing an aldehyde, an allyl alcohol and HN3 in a 1 3 9 ratio in presence of a Ti catalyst (Scheme 12). Allyl azido ethers 70, on thermolysis in benzene, proved to be ideal substrates for the formation of 2,5-dihydrooxazoles 71 in 66-90% yield. To show that oxazolines are formed via triazolines and not via an independent nitrene pathway, thermolysis of 70 was followed by NMR in hexadeuteriobenzene at 70 °C. 

Most of the methods describing the preparation of Emtricitabine (and Racivir) rely on the construction of 1,3-oxathiolane ring by reaction of glycoMdehyde or glyoxalic acid derivatives with mercaptoacetic add or mercaptoacetic aldehyde (which exists as 1,4-ditiane 154). For example, one of the first of syntheses of this type commenced from allyl alcohol which was silylated and then subjected to ozon-olysis to give glycoMdehyde derivative 155 (Schane 36) [142], Reaction of 155 with mercaptoacetic add afforded 1,3-oxathiolane 156, which was reduced with LiAlH(OtBu)3 or DIBAL and then acetylated to form 157. Finally, reaction of 157 with silylated fluorocytosine derivative 158 followed by deprotection led to the formation of racemic 8 (Racivir). 

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