Palladium-catalysed cyclisation and functionalisation of 1,1-diacetoxy-2,7-diene and 1,1-diacetoxy-2-en-7-yne derivatives

✍ Scribed by Cedric W. Holzapfel; Lizel Marais

• Publisher: Elsevier Science
• Year: 1998
• Tongue: French
• Weight: 175 KB
• Volume: 39
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(98)00169-5

✦ Synopsis

Thc palladium-catal)sed 'mctallo-cnc' cyclisation, cyclisatimVcarbon~lation. -vinylstannane coupling, and Pd(lll-catalyscd chloropalladation/carboc?clisation of l,l-diacctox?-2,7-dienc and l.l-diacetoxy-2-cn-7-Snc derivatives are described The c3clic enolacetate products could rcadil 5 be comcrted into tile corresponding atdeh~,dcs that are amenable to fimhcr translbrnlalion (O 1998 Elsevier Science Ltd. All rights reserved.

The palladium(0)-catalysed 'metatlo-ene' cyclisation ofacetoxy-2,7-dienes and -2-en-7-ynes, pioneered by Oppolzer and co-workers, ~ has proven to be a synthetically powerfitl means of producing a variety of fimctionalised five-membered ring systems. In an attempt to introduce differentiated additional functionality into the cyclised product, we explored the feasibility of allylic gemmal-diacetate starting materials for these 'metalloene' reactions Assuming a similar reaction mechanism (Scheme 1) for tile cyclisation of 1,l-diacetoxy-2.7dienes (1), tile products (3) would, in addition to an exocyclic methylene, contain an enolacetate moiety The latter is readily converted into the corresponding aldehyde (4) on treatment with mild base. ~ '~O ()Ac Pd(0)L n Ac HOAc ~ I ~~.pd OAc IlL n 4 Scheme 1 Et3 N MeOH 2 $ -HPdLnO ,\c ~ ()Ac 3 The allylic gem diacetate starting materials were readily prepared (Scheme 2) from the corresponding monoacetates 12 (5) by deacetylation, reaction with the Dess-Martin periodinane (DMP) oxidising agent ~ to thmish tile allyl aldehyde (6), and diacetate (7) formation on treatment with iodine (catalytic) in acetic anhydride)