Cyclische Aldehydderivate als Alkylierungsreagenzien, 1. Mitt. Acyclo‐ und Azaacycloanaloga von Nucleosiden

Abstract

Ringoffnung von 1,3-Dioxolan und von 3-Alkyl-l,3-oxazolidinen mit Acetylchlorid oder Trimethyliodsilan fuhrt zu den a-Halogenethem &2e. Diese stellen Alkylierungsreagenzien dar. Ihre Umsetzung mit Adenin, 6-Chlorpurin oder silyliertem Cytosin bnv. silylierten Uracilderivaten gibt die 2-Hydroxyethoxymethyl-bzw. 2-Acetarnidoethoxymethylverbindungen 4, 5 und 7. Cyclic Aldehyde Derivatives M Alkylatbg Reagents, I: Arydo nnd Azaaqdo Aaplogs of NucleosidesRing opening of 1,3-dioxolane and of 3-alkyl-l,3-oxazolidines with acetyl chloride or trirnethyliodosilane leads to the a-halogeno ethers 2a-2e. These are alkylating reagents. Their reactions with adenine, 6-chloropurine, silylated cytosine or silylated uracil derivatives gives the 2-(hydroxy)ethoxymethyl-or 2-(acetamido)ethoxymethyl compounds 4, 5 and 7.Cyclische Aldehydderivate wie 1 ,3-Dioxolane1' oder 3-Alkyl-1 ,3-oxazolidine2) geben unter Saurekatalyse mit reaktiven Olefinen wie Enolethern'*2) oder Enaminen3) in einer polaren Cycloaddition Perhydro-l,4-dioxepine und -1,4-diazepine. In einigen Ftillen wurde daneben auch die Bildung acyclischer Reaktionsprodukte beobachtet'). Mechanistisch betrachtet verlaufen diese Umsetzungen iiber das ringgeoffnete Produkt 2, das elektrophil mit dem Olefin reagiert'). 192 2 R' X 0365-6233/83~4146 $02.50/0 Q

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

“…However, Pd/C freshly prepared from Pd(OAc) 2 and activated charcoal according to Felpin [ 77 ] delivered consistent results (reaction time < 3 h). Although the Cbz-cleavage beside a benzyl moiety in alcohols as solvent is known (for selected examples of the chemoselective Cbz-cleavage of Bn, Cbz-protected amines see [ 78 – 80 ]), we only achieved high chemoselectivities in the presence of an excess of HCl.…”

Poly(ε‐caprolactone)–poly(isobutylene): A crystallizing, hydrogen‐bonded pseudo‐block copolymer

“…The preparation of ( 5 ) includes three steps starting from thymine 40, 41. The first step is the protection of the amino group between the two carbonyl groups using an excess of hexamethyldisilazane and a catalytic amount of trimethylchlorsilane.…”

The Silyl Method for the Synthesis of 1[-2(Phenoxy)ethyl]uracils

“…In the conditions of the silyl modification of the Gilbert-Johnson reaction α-halo ethers readily alkylate uracil in high yields even at room temperature in aprotic solvents of low polarity [1- 3,7].…”

“…It is based on the alkylation of 2,4-bis(trimethylsiloxy)pyrimidines with highly reactive alkyl halides such as α-halo ethers [1][2][3] or α-halo sugars [4,5]. It is thought [6] that the first product of the interaction of the alkylating agent and 2,4-bis(trimethylsiloxy)pyrimidine is a quaternary salt which readily loses a trimethylsilyl halide to give the N (1) -substituted 4-(trimethylsiloxy)pyrimidin-2(1H)-one.…”