Thiazoles aldehydes

This review collects a part of the results of work on the thiazole-aldehyde synthesis that has been carried out over several years by various individuals whose names are reported in the references. One of us (A.D.) would like to express to all of them his gratitude and appreciation for their contribution. Financial support came from the Progetto Finalizzato Chitnica Fine e Secondaria n. 2 (Rome), the Consiglio Nazionale delle Ricerche (CNR, Rome), the Ministero della University e della Ricerca Scientifica (MURST, Rome). One of us (A. M.) is grateful to the University of Ferrara for having been appointed as Lecturer in Organic Chemistry at the Faculty of Engineering. 

Thiazole-aldehyde synthesis Preparation of aldehydes from C-2 substituted thiazoles by thiazolyl-to-formyl conversion, see A. Dondoni, Carbohydrate synthesis via thiazoles, in Modem Synthetic Methods, R. Scheffold, ed., Verlag Helvetica Chimica Acta, Basel, 1992, p. 377 A. Dondoni, Acyclic diastereoselective synthesis using functionalized thiazoles. Routes to carbohydrates and related natural products, in New Aspects of Organic Chemistry, Z. Yoshida and Y. Ohshiro, eds., Kodansha, Tokyo, and VCH, Weinhcim, 1992, p. 105. 

Dondoni et al. prepared a 1-hydroxyethylene peptide using a thiazole-aldehyde synthesis starting from an amino acid.[38] The aldehyde is converted into an alkanoate by Wittig alkenation and reduction of the double bond (Scheme 18). Then, removal of the tert-bu-tyldimethylsilyl group gives the unsubstituted lactone. In the last step, the lactone is alkylated using the method reported by Kleinman and co-workers. 20 ... 

Scheme 18 Formation of 1-Hydroxyethylene Peptides using a Thiazole-aldehyde Synthesis1381 Bzl OTBDMS 1 MeOTf Bzl OTBDMS...

In general, the properties of these compounds and those of their benzenoid analogues are similar. Thus, isothiazole aldehydes and ketones behave normally and form the usual derivatives. Imidazole-2-carbaldehyde exists as a hydrate in aqueous solution. 4-Acetyloxazoles are oxidized to the corresponding acids with sodium hypobromite. Thiazole aldehydes undergo the benzoin and Cannizzaro reactions. Compounds with aldehyde groups to an NH group sometimes form dimers, e.g., as in the 1,2,4-triazole series 615. 

The thiazole-substituted homoallylic alcohol 25 (Scheme 6) is a key intermediate, not only for RCM strategies, but also for other routes. Thiazole aldehyde 4 (Chapter 3) after homologation to enal 24 (90 % yield) [ 11,20) was subjected to asymmetric allylation with allylboron and tin reagents. Interestingly 25 with identical absolute stereochemistry was synthesized by Nicolaou et al. with (+)-IpC2B(allyl) in 96 % yield and > 97 % ee [13, 20], and by Danishefsky et al. with the enantiomeric (—)-Ipc2B(allyl) in 83 % yield and > 95 % ee [11], i.e. in one case an er-... 

Hydroxy-4-hetarylthiazoles, from o-thio-cyanato-heteroarylketones, 273 2-HydtoxymethyM,5-dimethylthiazole, from 4,5-dimethylthiazole, 393 4-(Hydroxymethylthiazole), from 4-thiazole aldehyde, 341... 

Polarographic reduction of oxazole and thiazole aldehydes in alkaline conditions has been reported to give dimeric products, presumably by coupling of intermediate ketyls. ... 

Dondoni, A, Perrone, D, Total synthesis of (+)-galactostatin. An illustration of the utility of the thiazole-aldehyde synthesis, J. Org. Chem., 60, 4749-4754, 1995. 

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