vic-Iodothiocyanates and iodoisothiocyanates. Part 4. The synthesis of 2-substituted-2-thiazolines

Abstract

The reactions of trans-1 -iodo-2-isothiocyanatocyclohexane with a number of carbon nucleophiles to form 2substituted-2-thiazolines are described. Reactions of several vic-iodoisothiocyanates with butyl-lithium give products which are dependent on the solvent and/or temperature.IN preceding papers we have reported methods for the conversion of vic-iodoisothiocyanates into thiazolidin-2ones,l 2-amino-2-thiazolines,l and 2-alkoxy-2-thiazolines.2 We report here reactions of a representative vic-iodoisothiocyanate (1), with a series of carbon nucleophiles to form 2-cyano-, 2-alkyl-, and 2-aryl-2thiazolines. The latter compounds are of synthetic value since protons on carbon atoms attached to C-2 of the thiazoline nucleus are acidic; use has been made of this property by Meyers and his co-workers in the synthesis of protected carbonyl compounds. For example, the labile P-hydroxyaldehyde (4) is formed when the litliio-thiazoline (5) is treated with cyclohexanone and the thiazolinyl moiety is removed subsequently by reduction and mercury(I1)-catalysed hydrolysis. Hackler and Balko recently reported the preparation of two 2-alkyl-2-thiazolines from the reaction of carbon nucleophiles with vic-chloro-and vic-bromo-isothiocyanates but their products were obtained in only moderate yields (35% and 42%). RESULTS AND DISCUSSION/ P C l t SCHEME 1 out by examination of the mass spectrum, which showed fragmentation peaks corresponding to the loss of C1, CH,Cl, and SCH,Cl from the molecular ion, but not to TABLE 1 Reactions of trans-l-iodo-2-isothiocyanatocyclohexane H RM KCN p-OMeC,H,CZCLi PhCrCLi Me,SiCXLi MeMgI EtMgI BuMgBr PhLi Some products were prepared by several modifications ; Isolated by p.1.c. the loss of CN, CH,CN, or SCH,CN. Moreover, the use of 13C n.m.r. substituent chemical-shift values allows differentiation between the structures (2) and (3); the combined a-effect of a carbon bearing a sulphur and chlorine atom would afford a chemical shift of ca. 6c 51 (C1= +31, SR = +20) (observed 6c 42.5) compared with a chemical shift of ca. aC 24 (SR = +20, CN = +4) for a carbon bearing a sulphur atom and a nitrile group. the yield quoted is the highest obtained. After distillation.

Propyne Iminium Salts By N-Alkylation of Alkynyl Imines

“…The following starting materials were prepared according to literature procedures: 4aÐc, 22 7a, 23 1,4-diethynylbenzene, 24 (trimethylsilyl)acetyl-ene, 25 methyl trifluoromethanesulfonate. 26…”

Routes to N,N‘-Unsymmetrically Substituted 1,3-Diketimines

“…Indeed, by reacting imine 13 or 14 with imidoyl thioether 25 or 26 , we successfully prepared a series of N , N ‘-unsymmetrically substituted 1,3-diketimines, both cyclic and noncyclic, in 53−84% yield (Scheme and Table ). Imidoyl thioether electrophile 25 or 26 can be synthesized in high yield from numerous commercially available aliphatic amides via conversion to their thione derivatives, followed by alkylation 10 Routes to Diverse N , N ‘-Unsymmetrically Substituted 1,3-diketimines a a Reagents and conditions: (a) Lawesson's reagent or P 4 S 10 (88−89%); see ref ; (b) MeI or (MeO) 3 BF 4 (92−98%); see ref . …”

“…Imidoyl thioether electrophile 25 or 26 can be synthesized in high yield from numerous commercially available aliphatic amides via conversion to their thione derivatives, followed by alkylation 10 Routes to Diverse N , N ‘-Unsymmetrically Substituted 1,3-diketimines a a Reagents and conditions: (a) Lawesson's reagent or P 4 S 10 (88−89%); see ref ; (b) MeI or (MeO) 3 BF 4 (92−98%); see ref . …”

Synthese und Anwendung eines radioaktiven Photoaffinitätslabels zur Wirkortbestimmung von Naturstoffen sowie Beiträge zur Totalsynthese des Collinolactons

“…in Anlehnung an eine Literaturvorschrift von ITO et al [128] , mit iso-Propylmagnesium- Die Synthese des bekannten Bromides 166 und der dafür benötigten Edukte erfolgte nach literaturbekannten Vorschriften. Dabei wurde aus Acetylen und Iodbromid zunächst Iod-bromethylen [129] hergestellt, welches über eine Kreuzkupplung [130] mit Tetrakis(triphenylphosphin)palladium(0) [131] und TMS-Acetylen [132] das Bromid 166 ergab. Dieses wurde wiederum mit tert-Butyllithium lithiiert und anschließend mit Amid 164 versetzt.…”

“…Lösungsmittel wurden nach üblichen Laboratoriumsmethoden [ 168 ] Literaturvorschrift hergestellt: Zinn(II)triflat [ 169 ] ; 1-(4-Bromphenyl)-2,2,2-trifluorethanon [ 170 ] ; Formaldehyd/THF-Lösung [53] ; Kendomycin-Acetonid (81) [62] ; (tert-Butyldimethyl-silanyloxy)-acetaldehyd (141) [109] ; 4-Brom-crotonsäureethylester (147) [171b] ; Crotonsäureethylestertriphenylphosphoniumbromid (148) [ 171 ] ; 4-Brom-3-oxobutansäureethylesters (159) [117] ; 4-(Diethoxyphosphoryl)-3-oxobutansäureethylester (154) [120] ; 1-Iod-2-bromethylen [129] ; Tetrakis-(triphenylphosphin)palladium(0) [131] ; TMS-Acetylen [132] ; Z-(4-Methoxy)but-2-en-1-ol [172] ; Z-(4-Benzyloxy)but-2-en-1-ol [173] ; Z-(4-tert-Butylsilanyloxy)but-2-en-1-al (141 Z ) [135] ; E-(4-Benzyloxy)but-2-en-1-al (169) [134] ; Z-(4-Methoxy)-but-2-en-1-al (168) [136] ; 1,2-Bistrimethylsilyloxyethan [156] .…”