Thiocarbonyl ylides and electrophilic azo compounds; Sterically hindered cyclic hydrazodicarboxylic esters

✍ Scribed by Rolf Huisgen; Xingya Li; Grzegorz Mloston; Rudolf Knorr; Helmut Huber; David S Stephenson

• Book ID: 104209675
• Publisher: Elsevier Science
• Year: 1999
• Tongue: French
• Weight: 889 KB
• Volume: 55
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(99)00790-5

✦ Synopsis

The cycloadduct 5, prepared from adamantanethione S-methylide with dimethyl azodicarboxylate, exists in solution in two conformations P and Q (70:30 in CDCI3), which are selm~ted by a barrier of AG~ 18.3 + 0.6 kcal mol-I; according to NMR spectra, both forms are chiral. Steric hindrance to 3'N-CO2CH 3 rotation by the =dlrmmtane system generates CfO outside and CfO in-s~de conformations. The barrier to emmtiomerizatiun (AB ~ A 2 for 5'-H2) is higher (> 20.1 kcal tool-I). Three combinations of rate processes are discussed. Except for the 5'-methyl compound 19a, the chiral cycloadducts of four other thiocarbonyl ylides to dimethyl azodicarboxylate do not show dimtereoisomeric conformations in their NMR spectra at ambient temperature.