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%% This is a (brief) example using the beilstein class.
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%% If issues arise when submitting your manuscript, you may want to
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%% version of every file you have used. That way the maintainer of
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%%\listfiles
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%% The document class does not have many options yet. It accepts an
%% optional keyval option for the manuscript type and options for the
%% language and inputencoding used.
%% These are for the manuscript type:
%% manuscript=fullresearchpaper (default),
%% manuscript=letter,
%% manuscript=commentary,
%% manuscript=review,
%% manuscript=bookreport,
%% manuscript=suppinfo.
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%% For the language (in terms of hyphenation):
%% american -> American English (default),
%% british, english -> British English.
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%% For the input encoding:
%% latin1 (default),
%% utf8,
%% applemac.
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%% The defaults are [manuscript=fullresearchpaper,american,latin1].
%% Please note, that you should consider using the utf8 option as this
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\documentclass[utf8]{beilstein}
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%% Place any additional packages needed here. Only include packages
%% which are essential to avoid problems later. The class already
%% loads some useful packages, so please have a look at the
%% documentation.
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\usepackage{xspace}
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%% Place any additional macros here. Please use \newcommand* where
%% possible, and avoid layout-changing macros (which are not used
%% when typesetting).
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\newcommand*{\CHCL}{\chem{CH_2Cl_2}}
\newcommand*{\HNMR}{\chem{^{1}H~NMR}\xspace}
\newcommand*{\CNMR}{\chem{^{13}C~NMR}\xspace}
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%% Beginning of the article
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\begin{document}
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%% The title of the article is given with the usual \title command.
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%% If you write a file for supporting information using manuscript=suppinfo,
%% you should give an additional title using the macro \sititle or the
%% optional argument of \title
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%% Each author should be given as a separate \author command.
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%% For corresponding authors please use \author* and give the email
%% address as a second mandatory argument.
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%% The affiliation of authors is given after the authors; the
%% affiliations are numbered consecutively.
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%% If some authors have the same affiliation you can use the optional
%% argument of \author and \author* to give the number of that
%% affiliation.
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\title{Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes}
%%%\sititle{} % when using manuscript=suppinfo
\author*{Stephen P. Marsden}{s.p.marsden@leeds.ac.uk}
\affiliation{School of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom}
\author{Pascal C. Ducept}
\affiliation{Department of Chemistry, Imperial College London, London SW7 2AY, United Kingdom}
\maketitle
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%% The document should begin with an abstract, if appropriate. If one
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\begin{abstract}
\background Allenylsilanes are useful intermediates in organic synthesis. An attractive,
convergent but little used approach for their synthesis is the alkylidenation of stable silylketenes. Reactions thus far have been limited to the use of unsubstituted silylketenes (or equivalents) with stabilised or semi-stabilised ylides only. The current study explores the reactions of substituted ketenes prepared through rhodium(II)-mediated rearrangement of silylated diazoketones.
\results A range of novel 1,3-disubstituted and 1,3,3-trisubstituted allenylsilanes were prepared using stabilised and semi-stabilised ylides. Alkylidenation with non-stabilised phosphorus ylides was not viable, but the use of titanium-based methylenating reagents was successful, allowing access to 1-substituted allenylsilanes.
\conclusion Many novel allenylsilanes may be accessed by alkylidenation of substituted silylketenes. Importantly, for the first time, simple methylenation of silylketenes has been achieved using titanium carbenoid-based reagents.
\end{abstract}
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%% Keywords can be given with the \keywords command which takes five
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\keywords{allenylsilanes; rhodium(II) octanoate-mediated rearrangement; silylketenes; titanium carbenoids; ylide}
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%% The main text starts right here. For each required and optional
%% section of the chosen document type a special command is defined.
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%% It is strongly recommended to use BibTeX for managing references.
%% Citations and citation lists can be given with the \cite command.
%% Please note, that not all references have been added to the
%% example document.
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%% For references in floats \cite is locally redefined to
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\section{Introduction}
Allenylsilanes are versatile intermediates for organic synthesis \cite{Pornet2002,Masse1995}. They have two main modes of reactivity: firstly, as propargyl anion equivalents in thermal \cite{Jian1995,Weinreb1998} or Lewis acid-mediated \cite{Danheiser1980,Danheiser1986} addition to carbonyls, acetals and imines, and secondly as three-carbon partners in [3+2] annulation reactions. Thus, reaction with aldehydes \cite{Danheiser1985}, imines/iminiums \cite{Danheiser1985,Daidouji2005}, enones \cite{Danheiser1981,Danheiser1983,Danheiser1985b} and nitrosyl cations \cite{Danheiser1987} leads to dihydrofurans, dihydropyrroles, cyclopentenes and isoxazoles respectively \cite{Yadav2004}. In most cases the silicon is retained in the final product and can be used as a handle for further synthetic elaboration.
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%% When referencing objects, LaTeX offers a label--ref mechanism.
%% The beilstein class extends this approach with the \cref command,
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%% Tables, figures and schemes must have a single column or double
%% column width. To make life easier, some commands are defined.
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%% Captions (legends) will always be added at the correct place no
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Amongst the myriad methods to prepare allenylsilanes \cite{Pornet2002,Danheiser1987b}, an attractive disconnection is to consider a Wittig-type alkylidenation of a silylketene (\cref{fig:AlkylidenationApproach}).
\begin{figure}
\caption{Alkylidenation approach to the synthesis of allenylsilanes.}
\label{fig:AlkylidenationApproach}
\includegraphics[width=8.2cm,keepaspectratio]{figure1}
%% \sglcolfigure{figure1}
\end{figure}
[\ldots]
\section{Results and Discussion}
Our investigations began with the preparation of substituted silylketenes \CN{1} as substrates for the alkylidenation chemistry. This was carried out under our previously reported conditions for rhodium(II) octanoate-mediated rearrangement of silyl diazoketones \CN{2}, which in turn were prepared by \textit{C}-silylation of the parent diazoketones \CN{3} with triethylsilyl triflate (\cref{scheme:1}). It should be noted that while the alkyl-substituted silylketenes are relatively stable and show little decomposition at room temperature over several days, the (hetero)aromatic-substituted silylketenes are much less robust and should be used quickly or stored in a freezer.
\begin{scheme}
\caption{Synthesis of substituted silylketenes \CN{1}.}
\label{scheme:1}
\includegraphics[width=8.2cm,keepaspectratio]{scheme1}
\end{scheme}
[\ldots]
With the requisite silylketenes in hand, attention turned to their reaction with the carboethoxy-stabilised phosphoranes \CN{4} and \CN{5}. At the outset, it was by no means certain that these would react efficiently with substituted silylketenes \CN{1} since it is well documented that nucleophiles attack silylketenes \textit{anti} to the silicon, i.e.\ the phosphoranes would be approaching from the same side as the \chem{R^1}-substituent. Since in all previous examples this substituent has been a hydrogen atom, the extension to bulkier substituents could not be taken for granted. In the event, however, we were pleased to find that in nearly all cases the desired allenylsilanes were formed in moderate to excellent yield (\cref{scheme:2}, \cref{tab:1}, see \cref{si:1} for full experimental data).
\begin{scheme}
\includegraphics[width=8.2cm,keepaspectratio]{scheme2}
\caption{Reaction of substituted silylketenes with ester-stabilised phosphoranes.}
\label{scheme:2}
\end{scheme}
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%% Tables are a bit special. Only there the \footnote is allowed for
%% Beilstein publications.
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%% As for figures and schemes sglcoltabular and dblcoltabular can be
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\begin{table}
\caption{Reaction of substituted silylketenes with ester-stabilised phosphoranes.}
\label{tab:1}
\begin{dblcoltabularx}{|l|l|l|l|l|X|X|}\hline
\bfseries Entry & \bfseries Ketene & \bfseries Ylide & \bfseries Temp [\celsius] & \bfseries \textit{t} [h] & \bfseries Solvent & \bfseries Yield 6/7 (8)\\\hline
1 & \CN{1a} & \CN{4} & 80 & 24 & PhH & 54\,\%\\\hline
2 & \CN{1a} & \CN{5} & rt & 3 & \CHCL & 60\,\%\\\hline
3 & \CN{1b} & \CN{4} & 110 & 24 & toluene & 45\,\%\\\hline
4 & \CN{1b} & \CN{5} & reflux & 24 & \CHCL & 77\,\%\\\hline
5 & \CN{1c} & \CN{4} & 80 & 24 & PhH & 60\,\%\\\hline
6 & \CN{1c} & \CN{5} & rt & 6 & \CHCL & 81\,\%\\\hline
7 & \CN{1d} & \CN{4} & 110 & 48 & toluene & 22\,\%%
\footnote{60\,\% of starting material recovered}\\\hline
8 & \CN{1d} & \CN{5} & 80 & 48 & toluene & 78\,\%\\\hline
9 & \CN{1e} & \CN{4} & 80 & 24 & PhH & 55\,\% (7\,\%)\\\hline
10 & \CN{1f} & \CN{4} & 60 & 5 & \CHCL & 44\,\% (3\,\%)\\\hline
11 & \CN{1h} & \CN{4} & rt & 6 & \CHCL & 0\,\% (57\,\%)\\\hline
12 & \CN{1h} & \CN{4} & 50 & 1 & \CHCL & 7\,\% (23\,\%)\\\hline
13 & \CN{1i} & \CN{4} & rt & 10 & \CHCL & 0\,\% (67\,\%)\\\hline
14 & \CN{1i} & \CN{5} & rt & 2 & \CHCL & 98\,\%\\\hline
15 & \CN{1j} & \CN{4} & 80 & 12 & PhH & 74\,\% (19\,\%)\\\hline
\end{dblcoltabularx}
\end{table}
As expected, reactions with the more substituted ylide \CN{4} were significantly slower than those with the parent ylide \CN{5} (compare reaction temperatures and times, entries 1, 3 and 5 versus entries 2, 4 and 6). [...]
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%% The Supporting Information is an essential part of many articles.
%% They are given inside the ``suppinfo'' environment with the
%% \sifile command which gets the following mandatory arguments:
%% #1: File name
%% #2: File type
%% #3: Descriptive File title
%% A long description can be given using the optional argument.
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\begin{suppinfo}
Supporting information features copies of \HNMR spectra of silylated diazoketones \CN{2} and silylketenes \CN{1}, plus \chem{{}^1H} and \CNMR spectra of allenylsilanes \CN{6}, \CN{7}, and \CN{14}--\CN{19}.
\sifile{S1.pdf}{PDF}{Experimental part}\label{si:1}
\sifile{S2.pdf}{PDF}{NMR spectra of compounds \CN{1}, \CN{2}, \CN{6} and \CN{7}}
\sifile{S3.pdf}{PDF}{NMR spectra of compounds \CN{14--19}}
\end{suppinfo}
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\begin{acknowledgements}
We acknowledge EPSRC grant GR/L60135/01 (PCD) and generous unrestricted research funding from Pfizer for financial support.
\end{acknowledgements}
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\bibliography{beilstein-template}
\vspace{3cm}
This article is published in full length in \textit{Beilstein J. Org. Chem.}
\textbf{2005}, \textit{1}, No. 5.
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%% That's it. Ending the document finishes the article. Happy TeXing!
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\end{document}
