Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• ) [114]. 5.4. Parson. Radical cyclization The development of novel cascade (or domino) radical reactions is an active area of current research, and one approach to the mitomycin ring system focused on the application of 1-6-hydrogen atom transfer to create a pyrrolidinone radical, which could then

Radical cascades using enantioenriched 7-azabenzonorbornenes and their applications in synthesis

• David M. Hodgson and
• Leonard H. Winning

Beilstein J. Org. Chem. 2008, 4, No. 38, doi:10.3762/bjoc.4.38

• electrophile trapping with the sulfone corresponds approximately to the rate of hydrogen atom transfer from (TMS)3SiH. Attempted reaction with methyl vinyl ketone, N,N-dimethylacrylamide and methyl propiolate gave rearranged-reduced azacycle 8 in modest yields, as well as small quantities of hydrosilylated

Part 2. Mechanistic aspects of the reduction of S-alkyl- thionocarbonates in the presence of triethylborane and air

• Florent Allais,
• Jean Boivin and
• Van Tai Nguyen

Beilstein J. Org. Chem. 2007, 3, No. 46, doi:10.1186/1860-5397-3-46

• deuterium transfer is observed from either compounds 3, 4, or 5 when xanthate 1a was subjected to reduction (Method A) in the presence of one equivalent of O-ethyl-S-ethyl dithiocarbonate, using benzene as solvent to suppress any hydrogen atom transfer from the solvent. Along the same lines, we prepared

Part 1. Reduction of S-alkyl- thionocarbonates and related compounds in the presence of trialkylboranes/air

• Jean Boivin and
• Van Tai Nguyen

Beilstein J. Org. Chem. 2007, 3, No. 45, doi:10.1186/1860-5397-3-45

• following observations: – the attack of a carbon radical on the sulfur atom of a thiocarbonyl function is known to be a fast process; – the hydrogen atom transfer in the system Et3B/air is a relatively slow process as demonstrated above. In the case of S-alkylxanthates a, the production of radical R

• transfer is slow, the radical may easily react with a or e [equation (2)], thus establishing a degenerate process that does not consume the starting material a, preserves the radical character and allows slow hydrogen atom transfer to occur. For O-alkylxanthates, the situation is different. The reaction of

• Et• with f gives rise to h and R• [equation (3)]. If the hydrogen atom transfer is slow, the latter reacts with f to afford the rearranged S-alkyl S-methyldithiocarbonate j. As R• radical cannot react with the carbonyl function of j, the starting material is progressively consumed by the unwanted

Do α-acyloxy and α-alkoxycarbonyloxy radicals fragment to form acyl and alkoxycarbonyl radicals?

• Dennis P. Curran and
• Tiffany R. Turner

Beilstein J. Org. Chem. 2006, 2, No. 10, doi:10.1186/1860-5397-2-10

• atom transfer (Figure 2). The resulting radical 5 rebounds back to the enol ether in a 1,5-cyclization to provide 6. In the crucial self-terminating step, radical 6 is suggested to fragment to product 2 and radical X•. Related steps are involved in the formation of ketone 3 (not shown), except that the

• . Representative reagents, reactions conditions and product yields for this very general transformation are shown in Figure 1. The suggested mechanism for formation of 2 involves addition of an oxygen-centered radical (XO•) to 1 to generate vinyl radical 4, followed by rapid radical translocation by 1,5-hydrogen